Development of Catalytic Generation and Its Application to Organic Synthesis

Yasutaka Ishii * and Satoshi Sakaguchi

Department of Applied •¬ High Technology Research Center; Faculty of Engineering Kansai University,

Received June 30, 2003

Abstract: Innovative carbon radical generation from hydrocarbons through a catalytic process under mild conditions has been achieved by the use of N-hydroxyphthalimide (NHPI) as a catalyst. This method can be successfully applied to a wide variety of functionalizations of hydrocarbons. Thus, are converted into alcohols, ketones, carboxylic acids, nitro alkanes and alkyl sulfonic acids through alkyl radicals generat- ed by the action of NHPI. Hydroxysilylation was first performed by the addition of hydrosilanes and to alkenes bearing electron-withdrawing substituents. A new approach to oxyalkylation based on the con- comitant addition of carbon radicals derived from alkanes or alcohols and molecular oxygen to alkenes or alkynes has been described.

Scheme 1. General method for alkyl radical generation 1. Introduction Although various methodologies have been developed for the generation of carbon radicals, most of these are inappli- cable to the generation of alkyl radicals from alkanes. For the generation of alkyl radicals, the reaction of alkyl halides with tributyltin hydride or tris(trimethylsilyl)silane in the presence of a radical initiator like AIBN is frequently used. Thermal decomposition of Barton esters or acyl peroxides is also used (Scheme 1).1 These methods are stoichiometric reactions and are limited to use in laboratory-scale synthesis. Aerobic oxi- dation of cycloalkanes like cyclohexane using a radical initia- tor in the presence of the Co ion which proceeds through the formation of carbon radicals is applied to the autoxidation in industrial chemistry.2 However, the efficiency of the genera- tion of alkyl radicals by this method is not high in spite of the performance at higher temperature (150-180t). This is because the reaction under such temperature results in homolysis not only of the desired C-H bonds but also of Scheme 2. Alkyl radical generation by NHPI undesired C-C bonds, which have lower bond energy than C-H bonds. There has been long-standing interest in the generation of alkyl radicals from alkanes under mild condi- tions. Therefore, the development of selective methodology for carbon radical generation from hydrocarbons, especially alkanes, is a very important area in organic synthesis, since over 90% of organic chemicals are derived from petroleum whose main constituent is saturated hydrocarbons. We have recently found that phthalimide N-oxy (PINO) radical, generated from N-hydroxyphthalimide (NHPI), serves as a carbon-radical-producing-catalyst from alkanes, alkenes, alcohols, ethers, acetals, and aldehydes to the corre- sponding carbon radicals. By the use of NHPI as the cata- lyst, alkanes can be functinalized to oxygen-containing com- pounds like alcohols, ketones and carboxylic acids, nitroalka- nes, and alkylsulfonic acids under mild conditions (Scheme 2).3 In this account, we describe recent applications of NHPI to synthetic reaction. ly carried out in industrial scale in the presence of a Co ion 2. Oxidation of Alkylbenzenes at 130 to160•Ž.4 However, we first achieved the oxidation of toluene to benzoic acid under normal pressure (1 atm) of O2

The aerobic oxidation of toluene to benzoic acid is current- at temperature (25t) by the use of NHPI combined with

1056 ( 16 ) J. Synth. Org. Chem., Jpn. Co(OAc)2 as the catalyst (Scheme 3).5 It is interesting to note (NAPI), or N, N', N"-trihydroxyiminocyanuric acid that replacement of Co(II) by Co(III) under these conditions (THICA) as key catalysts. In the oxidation of p-xylene cat- failed to initiate the oxidation at room temperature. A labile alyzed by NHPI, obtaining over 80% yield of terephthalic dioxygen complex such as superoxocobalt(III) or peroxo- acid in a one-step reaction required 20 mol% of catalyst, cobalt(III) complexes is known to be formed by the complex- whereas the catalyst was reduced to 10 mol% by the use of ation of Co(II) with 02. However, since no cobalt-oxygen NAPI. We found that THICA is more active than these cata- complex, which is necessary to initiate the reaction, is not lysts, and that terephthalic acid is obtained in high yield generated from the Co(III) and 02, the NHPI/Co(III) system (> 95%) even by the use of only 3 mol% of THICA.6 does not catalyze the oxidation at room temperature. At higher temperature, Co(III) is gradually reduced to Co(II) by Scheme 4. Aerobic oxidation of p-xylene a substrate like toluene via one-electron transfer process, and the reduced Co(II) reacts with 02 to form the Co(III)-oxygen complex which can initiate the reaction. Consequently, an induction period was observed in the oxidation when the NHPI/Co(III) system was employed. It is important to note that hydrocarbons such as toluene could be catalytically oxi- dized by atmospheric dioxygen at room temperature.

Scheme 3. Aerobic oxidation of toluene

Carboxylic acids obtained by oxidation of the side chains of alkyl heterocyclic compounds are widely used as raw mate- rials in pharmaceuticals and dyes synthesis. For example, nicotinic acid obtained by the oxidation of picoline is a very important intermediate for synthesizing vitamins. At present, nicotinic acid is manufactured by the oxidation of 5-ethyl-2-methylpyridine with nitric acid, but the nitric acid oxidation brings about the evolution of air pollution gases like N20. Although the aerobic oxidation of picoline by a Co/Mn/Br catalyst has been reported, the reaction conditions are harsh and selectivity is low.7

β-Picoline was oxidized to nicotinic acid (77%) in the pres- ence of catalytic amounts of NHPI, Co(OAc)2 and Mn(OAc)2 under 02 (1 atm) in acetic acid (eq. 1).8a The reaction using the NHPI/Co/Mn catalyst is a pollution-free reaction process which is industrially useful. 3-Quinoline carboxylic acid derivatives have pharmacological activities and exist widely in nature. These acids are now synthesized by the oxidation of methylquinolines with heavy metal salts such as KMnO4 and Cr03. Until now, there has been no successful oxidation of quinolines with molecular oxygen as an oxidant. We devel- oped a novel oxidation method of 2-methylquinoline with 02 by adding a small amount of NO2 to NHPI in the absence of any metal catalysts.Sb 3-Methylquinoline was first successfully oxidized to the corresponding carboxylic acid (75%) with 02 using NHPI and NO2 as catalysts (eq. 2).

(1) Terephthalic acid is manufactured on a large scale as raw material for the production of PET resin. The oxidation is usually carried out under 15-30 atm of air at 175-225•Ž using the Co/Mn/Br system as catalyst.4 This method, howev- (2) er, has several drawbacks such as emission of bromine into the atmosphere, formation of brominated products, and cor- rosion of the reactor by the bromide ion. Hence, it is desir- able to develop a bromine-free catalytic system. We succeed- 3. Aerobic Oxidation of Alkanes ed in a bromine-free aerobic oxidation system of p-xylene to terephthalic acid by the use of NHPI, N-acetoxyphthalimide To date, over two million tons of adipic acid have been

Vol.61 No.11 2003 ( 17 ) 1057 manufactured worldwide annually as a raw material for using NHP1/Co(II) catalyst in benzonitrile under air pressure 6,6-nylon. The current production of adipic acid consists of (10 atm) yielded tert-butyl alcohol in 80% yield (eq. 4).14 a two-step process involving Co-catalyzed autoxidation of Scheme 5. Aerobic oxidation of adamantane cyclohexane to a cyclohexanone/cyclohexanol (K/A oil) and the nitric acid oxidation of the K/A oil to adipic acid.9 This method was industrialized by Du Pont in 1940, and in princi- ple, is still being used today. In order to avoid side reactions in the first step, it is necessary to keep the conversion of cyolohexane into a K/A oil down to only 3-6%. The oxida- tion with nitric acid in the second step evolves a large amount of undesired global-warming substances like N20. Therefore, the direct conversion of cyclohexane to adipic acid with 02 has long been sought as a promising method in industrial chemistry worldwide. Cyclohexane could be oxidized to adipic acid in one step with 02 (1 atm) by using NHP1 combined with a small amount of Mn salt (eq. 3).1° Although the oxidation did not (4) take place by NHPI alone, adipic acid was obtained by adding a small amount of Mn salt (0.5 mol%) to the NHPI in high conversion (70%) and selectivity (70%). The oxidation 4. Oxidation of Alkenes and Alkynes with Molecular of cyclohexane was successfully achieved without any sol- Oxygen vents. Since NHPI is difficult to dissolve in cyclohexane, cyclohexane cannot be oxidized by NHPI without solvents. 4.1 Epoxidation of Alkenes with in situ Generated By preparing a lipophilic NHPI derivative which dissolves in Peroxide cyclohexane, however, cyclohexane was oxidized under air A well-known method for the epoxidation of alkenes like with extremely high catalytic efficiency (Figure 1).11 propylene is the Halcon process which comprises a two-step process involving the oxidation of ethylbenzene to ethylben- zene and the Mo-catalyzed epoxidation using (3) the hydroperoxide obtained above.4 The oxidation of secondary alcohols with 02 by NHPI affords hydrogen peroxide and ketones.15 Hydrogen peroxide produced by this reaction was used for epoxidation of alkenes. The reaction of cis-2-octene under an oxygen atmo- sphere in the presence of 1-phenyletanol catalyzed NHPI and hexafluoroacetone (HFA) gave cis-1,2-epoxyoctane in 86% yield (eq. 5).16The epoxidation of cis-olefins using aldehydes and 02 results in a mixture of cis- and trans-epoxides, since the reaction proceeds via a radical process. However, the stereospecific epoxidation of cis-olefin by 02, which is gener- ally difficult to carry out, could be performed by the present method via in situ generation of H202 from alcohols by the Figure 1. Oxidation of cyclohexane catalyzed by NHPI derivatives without solvent. use of NHPI and HFA as catalysts.'7

Adamantane derivatives are very useful raw materials for high performance materials. The oxidation of adamantanes with molecular oxygen has been examined, but sufficient yields of oxygenated adamantanes have not yet been (5) obtained. The oxidation of adamantane in the presence of the NHP1/Co(II) catalyst under 02 produced adamantanols in 83% yield with a small amount of adamantanone (2%) (Scheme 5).12The ratio of mono-alcohol to diol can be con- trolled by choosing the reaction conditions. This epoxidation involves (i) in situ generation of hydrogen Although tert-butyl alcohol is currently produced by peroxide via a-hydroxyhydroperoxide (A) from an alcohol acid-catalyzed hydration of isobutene, a more rational and 02, and (ii) the epoxidation of alkenes by a-hydroxyhy- method for producing tert-butyl alcohol is the direct oxida- droperoxide (B) derived from hydrogen peroxide and HFA tion of isobutane with air. The conventional autoxidation of (Scheme 6). isobutane is aimed at the synthesis of tert-butyl hydroperox- The oxidation of secondary alcohols by the NHPI catalyst ide.13 The oxidation is operated at around 200°C under air is also utilized as an excellent synthetic method of hydrogen pressure (10 atm) to form tert-butyl hydroperoxide (about peroxide.15 75%), tert-butyl alcohol (about 21%), and (about 4.2 Aerobic Oxidation of Alkynes 2%) with a conversion of 8%. The oxidation of isobutane The dissociation energy of the propargylic C-H bond of

1058 ( 18 ) J. Synth . Org . Chem . , Jpn . Scheme 6. Epoxidation of alkenes

First sks

Second Step

alkynes is about 85 kcal mol-1, almost equal to that of the anol was reacted under 02 (1 atm) in the presence of small benzylic C-H bond of toluene (•` 87 kcal mo1-1).18 The oxida- amounts of NHPI and AIBN in CH3CN at 75•Ž followed by tion of alkynes with 02 by NHPI, therefore, is expected to treatment with InCl3 catalyst at room temperature, giving yield the corresponding ƒ¿-alkynyl ketones in which the ε-caprolactone in fair yield. propargylic are selectively oxidized. There has been little study on the selective introduction of an oxygen func- Scheme 7. Baeyer-Villiger oxidation of K/A oil tion to the propargylic position of alkynes except for an oxi- dation by Se02 using tert-BuOOH as an oxidant.19 Alkynyl ketones are usually synthesized by a coupling reaction of a metal acetylide with an acyl compound. The reaction of

4-octyne with 02 in the presence of NHPI (10 mol%) in ace- tonitrile occurred at room temperature to give 4-octyn-3-one in 75% yield (eq. 6).20 This is the first successful introduction of molecular oxygen to alkynes.

Peroxydicyclohexylamine (PDHA) was obtained with good

(6) selectivity by aerobic oxidation of K/A oil, followed by treat- ment of the resulting reactant with ammonia gas (eq. 7).22

PDHA is known to be easily converted to ƒÃ-caprolactam in

good yield.23 This reaction is a novel method for the synthe- sis of a ƒÃ-caprolactam precursor without formation of unde- 5. Aerobic Oxidation of K/A oil sired ammonium sulfate as a by-product.

K/A oil, a mixture of cyclohexanone and cyclohexanol, is an important raw material for the production of ƒÃ-caprolac- tone and adipic acid.9 A catalytic Baeyer-Villiger oxidation of cyclohexanone to ƒÃ-caprolactone using molecular oxygen remains as an unsolved reaction. In industry, ƒÃ-caprolactone is manufactured by Baeyer-Villiger oxidation of cyclohex- anone with peracetic acid. From both synthetic and industri- (7) al points of view, it is very attractive that the K/A oil can be used as the starting material for the production of ƒÃ-capro- lactone with 02 via a catalytic process. To our best knowl- edge, there are no reports on the catalylic Baeyer-Villiger oxidation of K/A oil with 02. 6. Functionalizations of Alkanes using NHPI Catalyst Our strategy is outlined in Scheme 7.21 The NHPI-cat- alyzed oxidation of cyclohexanol with 02 gives cyclohex- 6.1 Carboxylation of Adamantane anone and hydrogen peroxide through the formation of The carboxylation of saturated hydrocarbons with carbon a-hydroxyhydroperoxide (A) as an intermediate (path 1). monoxide and 02 is usually difficult to carry out efficiently.24

Treatment of the resulting mixture with an appropriate Lewis Radical carboxylation of adamantanes by a CO/02 system acid would provide ƒÃ-caprolactone (path 2). The K/A oil using NHPI as a catalyst was achieved with relatively high consisting of a 1:2 mixture of cyclohexanone and cyclohex- selectivity. The reaction of adamantane in the presence of

Vol.61 No.11 2003 ( 19 ) 1059 NHPI (10 mol%) and CO/air (15/1 atm) yielded 1-adamn- at 80t produced cyclohexanone oxime in one step (Scheme tane carboxylic acid and a small amount of dicarboxylic acid 10). This reaction is thought to be an attractive route to (eq. 8).25 oxime synthesis which does not produce any salts. Atom effi- ciency of this reaction is very high, since the tert-butyl nitrite used is easily produced from NO2 and tert-butyl alcohol which is recovered after the reaction. (8)

Scheme 9. Sulfoxidation of alkanes

6.2 Catalytic Nitration and Sulfoxidation of Alkanes In contrast to nitration and sulfoxidation of aromatic hydrocarbons where these methodologies have already been established, work on the nitration and sulfoxidation of alka- nes remains at a less satisfactory level. For example, the nitration of alkanes is run at higher temperatures (250-400t) using nitric acid or NO2 as the nitrating agent, but under such high temperatures, higher alkanes undergo not only homolysis of the C-H bonds but also cleavage of Scheme 10. Oximation of cyclohexane the C-C skeleton.26 Conventional nitration of cyclohexane by NO2 at 240t gives nitrocyclohexane in, at most, 16% yield.27 Cyclohexane was nitrated with NO2 under air in the pres- ence of a catalytic amount of NHPI at 70t to give nitrocy- clohexane in 70% yield (Scheme 8).28 In this reaction, NHPI could be recovered almost quantitatively by simple filtration after the nitration. We have also successfully performed the nitration using nitric acid in place of NO2 as the nitrating agent.29

Scheme 8. Nitration of alkanes

7. Generation of Alkyl Cations from Alkanes monoxide (NO) is a diatomic molecule which exists as a radical. If PINO can be generated from NHPI upon treatment with NO, a new reaction of alkanes with NO may be possible. The reaction of adamantane with NO in the presence of the NHPI in benzonitrile containing a small amount of acetic acid afforded N-1-adamantyl benzamide in 65% yield (Scheme 11).32aUnder the same conditions, phtha- lane was converted into phthalaldehyde (Scheme 12).32b These reactions can be rationally explained by assuming car- bocations as transient intermediates. It is reported that the sulfoxidation of alkanes by the use An alternative method to generate alkyl cations from alkyl of SO2 and 02 under photo-irradiation leads to alkylsulfonic radicals was confirmed by allowing alkanes to react with acids in low yields.3° We found that the reaction of adaman- cerium ammonium nitrate (CAN) in the presence of NHPI tane with a 1:1 mixture of SO2 (0.5 atm) and 02 (0.5 atm) (Scheme 13).33 Thus, alkylbenzenes underwent the Ritter- under the influence of catalytic amounts of VO(acac)2 and type reaction with nitriles to form amides in fair to good NHPI affords adamantanesulfonic acid in good yield yields. (Scheme 9).31 In addition, this reaction was found to be cat- 8. Utilization of NHPI as Polarity-Reversal Catalyst alyzed by VO(acac)2 even in the absence of NHPI. Lower alkanes such as propane were also sulfoxidated by this By intermolecular radical-chain addition of aldehydes to method at room temperature. alkenes, it is difficult to obtain simple aliphatic ketones, 6.3 Oximation of Alkanes because the hydrogen abstraction from aldehydes by adduct Cyclohexanone oxime, which is a raw material for the pro- radicals, derived from the addition of acyl radicals to alkenes, duction of 6-nylon, is manufactured by the reaction of cyclo- is an unfavorable reaction. hexanone with a salt of hydroxylamine with sulfuric acid. The reaction of aldehydes with alkenes in the presence of However, by this method the formation of a large amount of BPO and NHPI afforded the corresponding ketones in good undesired salts like ammonium sulfate is unavoidable. The yields. The reaction is considered to proceed through a reac- reaction of cyclohexane with tert-butyl nitrite in acetic acid tion path shown in Scheme 14.34 In this reaction, NHPI

1060 ( 20 ) J. Synth . Org . Chem . , Jpn . Scheme 11. Reaction of adamantane with NO hydrogen atom from NHPI than that from an aldehyde, lead- ing to the smooth production of an adduct ketone.

Scheme 14. Hydroacylation of alkenes

Scheme 12. Reaction of phthalane with NO

9. Oxyalkylation of Alkanes and Alkynes

Radical coupling reaction is a very useful means for form-

ing a new C-C bond in organic synthesis. Since alkyl radicals

can be easily generated from alkanes using the NHPI/02 sys-

tem, we examined the capture of alkyl radicals by alkenes

and 02. Adamantane was reacted with methyl acrylate in the

presence of the NHPI/Co(acac)3 catalyst under air. An oxyalkylated coupling product involving oxygen was obtained

in a good yield. The reaction can be explained by the addi-

tion of an adamantyl radical to methyl acrylate followed by Scheme 13. Ritter-type reaction of alkanes trapping of the resulting adduct radical by 02 (Scheme 15).35

This reaction is referred to as oxyalkylation of alkenes with

alkanes and molecular oxygen.

The addition of 1,3-dioxolane and dioxygen to methyl

acrylate smoothly progressed even at room temperature using

the NHPI/Co(OAc)2 system to yield ƒÀ-hydroxyacetal

(Scheme 16).36 Treatment of the formed acetal with acid led to the corresponding aldehyde in good yield. Therefore, this reaction is regarded as the addition of a formyl radical to

alkenes which is difficult to carry out by conventional meth-

ods (Run 4).

As shown in Scheme 6, the NHPI/02 system induces the

generation of ƒ¿-hydroxy carbon radicals from alcohols, and we attempted to capture them by ƒ¿,ƒÀ-unsaturated esters. The

reaction of 2-propanol with methyl acrylate in the presence

of a catalytic amount of NHPI and Co(OAc)2 under 02 pro-

duced ƒ¿-hydroxy-ƒÁ- dimethyl-ƒÁ- butylolactone (Scheme

17).37 This reaction involves the following steps: (i) hydrogen

abstraction from an alcohol by PINO to an ƒ¿-hydroxy car-

bon radical A, (ii) addition of A to methyl acrylate leading to

an adduct radical B, (iii) formation of diol C by the reaction

of B with 02, and (iv) intramolecular cyclization of C leading

to a lactone. serves as a polarity-reversal catalyst, i.e., an adduct radical, 10. Hydroxysilylation of Alkenes with Et3SiH and 02 generated by the addition of an acyl radical to an alkene, having a nucleophilic character can abstract more easily the The hydrosilylation of alkenes and alkynes with hydrosi-

Vol.61 No.11 2003 ( 21 ) 1061 Scheme 15. Oxyalkylation of alkenes Scheme 17. Hydroxylactone synthesis

lanes catalyzed by transition metal complexes is a major route to complex organosilanes. However, simultaneous intro- duction of both silyl and hydroxy functions to carbon-car- bon multiple bonds, which can be referred to as hydroxysily- lation, has remained an unsolved issue (Scheme 18).

Scheme 18 Scheme 16. Addition of 1,3-dioxolanes to alkenes

We have found that the hydroxysilylation of electron-defi-

cient alkenes with Et3SiH and 02 (1 atm) is promoted in the

presence of catalytic amounts of NHPI combined with a Co species (Scheme 19).38 The reaction is initiated by the abstrac-

tion of the hydrogen atom from Et3SiH by PINO to form tri-

ethylsily1 radical Et3Si•E which then adds to alkene to give an

adduct radical which is readily captured by dioxygen, afford-

ing a hydroxysilylated product.

Scheme 19. Hydroxysilylation of alkenes

1062 ( 22 ) J. Synth . Org . Chem ., Jpn . 11. Conclusion Org. Process Res. Dev. 1999, 3, 455. 8) (a) Shibamoto, A.; Sakaguchi, S.; Ishii, Y. Org. Process Res. We found that NHPI acts as a Carbon-Radical-Producing-Cat- Dev. 2000, 4, 505. (b) Sakaguchi, S.; Shibamoto, A.; Ishii, Y. alyst (CRPC) from the C-H bond of alkanes, alkenes, alco- Chem. Commun. 2002, 180. hols, ethers, acetals, and aldehydes under relatively mild con- 9) (a) Davis, D. D. "Ullman's Encyclopedia of Industrial Chemistry" Gerhartz, W. Eds., 5th ed.; John Wiley and Sons: New York, ditions. By the use of NHPI as a key catalyst, efficient and 1985, Vol. Al, pp.270-272. (b) Sato, K.; Aoki, M.; Noyori, R. selective functionalization reactions of hydrocarbons includ- Science 1998, 281, 1646. ing oxidation, carboxylation, nitration, sulfoxidation, and 10) (a) Ishii, Y.; Iwahama, T.; Sakaguchi, S.; Nakayama, K.; Nishiyama, Y. J. Org. Chem. 1996, 61, 4520. (b) Iwahama, T.; oximation, which have been difficult to be carried out so far, Shoujo, K.; Sakaguchi, S.; Ishii, Y. Org. Proc. Res. Dev. 1998, 2, were developed. The NHPI-catalyzed oxidation of K/A oil, a 255. mixture of cyclohexanone with cyclohexanol, could be 11) Sawatari, N.; Yokota, T.; Sakaguchi, S.; Ishii, Y J. Org. Chem. applied to the synthesis of ƒÃ-caprolactone and ƒÃ-caprolactam 2001, 66, 7889. 12) Ishii, Y.; Kato, S.; Iwahama, T.; Sakaguchi, S. TetrahedronLett. precursors which are very important materials in industrial 1996, 37, 4993. chemistry. Additionally, the reaction for concomitant intro- 13) Winlker, D. E.; Hearne, G. W. Ind. Eng. Chem. 1961, 53, 655. duction of alkyl radicals and O2 to alkenes which can be 14) Sakaguchi, S.; Kato, S.; Iwahama, T.; Ishii, Y Bull. Chem. Soc. referred to as oxyalkylation, has been established. Jpn. 1998, 71, 1237. 15) Iwahama, T.; Sakaguchi, S.; Ishii, Y. Org. Process Res. Dev. α-Hydroxy-γ-lactones, which are very difficult to be synthe- 2000, 4, 94. sized by conventional methods, are easily prepared by the 16) Iwahama, T.; Sakaguchi, S.; Ishii, Y. Chem. Commun. 1999, 727. reaction of alcohols, alkenes and O2 under the influence of 17) Mukaiyama, T.; Takai, T.; Yamada, T.; Rhode, O. Chem. Lett. the NHPI catalyst. The same strategy could be applied to the 1990, 1661. 18) Golden, D. M. Ann. Rev. Phys. Chem. 1982, 33, 493. reaction of 1,3-dioxolanes, masked aldehydes, alkenes and O2 19) Chabaud, B.; Sharpless, K. B. J. Org. Chem. 1979, 44, 4202. to form three-component coupling products in which oxygen 20) Sakaguchi, S.; Takase, T.; Iwahama, T.; Ishii, Y. Chem. functions are incorporated. Finally, the NHPI catalyst was Commun. 1998, 2037. found to promote the generation of silyl radicals from alkyl 21) Fukuda, 0.; Iwahama, T.; Sakaguchi, S.; Ishii, Y Tetrahedron Lett. 2001, 42, 3479. silanes. Thus, the first hydroxysilylation of alkenes with 22) Yamamoto, S.; Sakaguchi, S.; Ishii, Y. Green Chemistry 2003, 5, Et3SiH and O2 (1 atm) has been established. 300. Acknowlegments We acknowledge that these studies were 23) Reddy, J. S.; Sivasanker S.; Ratnasamy P. J. Mol. Catal. 1991, 69, 383. carried out in collaboration with co-workers at Kansai Uni- 24) (a) Barton, D. H. R.; Doller, D. Acc. Chem. Res. 1992, 25, 504. versity. These studies were supported in part by a (b) Arndtsen, B. A.; Bergman, R. G., Mobley, T. A.; Peterson, Grant-in-Aid for Scientific Research from the Ministry of T. H. Acc. Chem. Res. 1995, 28, 154. Education, JSPS Research for the Future Program of Japan 25) Kato, S.; Iwahama, T.; Sakaguchi, S.; Ishii, Y. J. Org. Chem. 1998, 63, 222. Society for the promotion of Science, and Daicel Chemical 26) Markofsky, S. B. "Ullmann's Encyclopedia Industrial Organic Industries, Ltd. Chemicals" Wiley-VCH: Weinheim, 1999; Vol.6, p.3487. 27) Bachman, G. G.; Hass, B. H.; Addison M. L. J. Org. Chem. 1952, 17, 914. References 28) Sakaguchi, S.; Nishiwaki, Y.; Kitamura, T.; Ishii, Y. Angew. 1) (a) Curran, D. P."Comprehensive Organic Synthesis" Ed by Chem. Int. Ed. Engl. 2001, 40, 222. Trost, B.; Fleming, I. M.; Pergamon, 1991,Vol. 4, Chapters 4.1 29) Isozaki, S.; Nishiwaki, Y; Sakaguchi, S.; Ishii, Y Chem. Com- and 4.2 (b) Ryu, I.; Sonoda, N.; Curran, D. P. Chem.Rev. 96, mun. 2001, 1352. 172 (1996).(c) Renaud, P.; Sibi, M. P. "Radicalsin OrganicSyn- 30) (a) Bjellqvist, B. Acta. Chem. Scand. 1973,27, 3180. (b) Fergu- thesis"Wiley-VCH, 2001, Vol. 1, Basic principles, and Vol. 2, son, R. R.; Crabtree, R. H. J. Org. Chem., 1991, 5503. (c) Crab- Applications. tree, R. H.; Habib, A. Comprehensive Organic Synthesis Vol 7; 2) (a) Sheldon, R. A.; Kochi, J. K. "Metal-CatalyzedOxidations of Trost, B. M. Ed.; Pergamon Press: New York, 1991, p.14, and OrganicCompounds" Academic Press, 1981.(b) Hill, C. L. "Acti- references sited therein. vationand Functionalizationof Alkanes"Academic Press, 1989. 31) Ishii, Y; Matsunaka, K.; Sakaguchi, S. J. Am. Chem. Soc. 2000, (c) "The Activationof Dioxygenand HomogeneousCatalytic Oxida- 122, 7390. tion", Ed by Barton, D. H. R.; Martell, A. E.; Sawyer,D. T. 32) (a) Sakaguchi, S.; Eikawa, M.; Ishii, Y Tetrahedron Lett. 1997, Plenum Press, 1993. 38, 7075. (b) Eikawa, M.; Sakaguchi, S.; Ishii, Y. J. Org. Chem. 3) Ishii, Y.; Sakaguchi, S.; Iwahama, T. Adv. Synth. Catal. 2001, 1999, 64, 4676. 343, 393. 33) Sakaguchi, S.; Hirabayashi, T.; Ishii, Y. Chem. Commun. 2002, 4) Parshall, G. W.; Ittel, S. D. "HomogeousCatalysis" 2nd ed.; 516. John Wiley and Sons: New York, 1992,p. 255. 34) Tsujimoto, S.; Iwahama, T.; Sakaguchi, S.; Ishii, Y. Chem. Com- 5) Yoshino, Y; Hayashi, Y; Iwahama, T.; Sakaguchi, S.; Ishii, Y. mun. 2001, 2352. J. Org. Chem.1997, 62, 6810. 35) Hara, T.; Iwahama, T.; Sakaguchi, S.; Ishii, Y. J. Org. Chem. 6) (a) Tashiro, Y; Iwahama, T.; Sakaguchi,S.; Ishii, Y. Adv.Synth. 2001, 66, 6425. Catal. 2001, 343, 220. (b) Hirai, N.; Sawatari, N.; Nakamura, 36) Hirao, K.; Iwahama, T.; Sakaguchi, S.; Ishii, Y. Chem. Commun. N.; Sakaguchi, S.; Ishii, Y. J. Org.Chem. 2003, in press. 2000, 2457. 7) (a) Davis, D. D. "Ullman,sEncyclopedia of Industrial Chemistry" 37) Iwahama, T.; Sakaguchi, S.; Ishii, Y. Chem. Commun. 2000, 613. W. Gerhartz, Eds., 5th ed.; John Wiley and Sons: New York, 38) Tayama, O.; Iwahama, T.; Sakaguchi, S.; Ishii, Y. Eur. J. Org. 1985,Vol. A27, p.587. (b) Mukhopadhyay,S.; Chandalia, S. B. Chem., 2003, 2286.

Vol.61 No.11 2003 ( 23 ) 1063 PROFILE

Yasutaka Ishii was born in Osaka, Japan, in 1941, graduated from Kansai University in 1964. He received his Ph.D. degree under the supervision of Prof. Masaya Ogawa. In 1967, he was appointed assistant professor at Kansai University. He was a postdoctoral fellow at Colorado State University in 1980- 1981. Since 1990 he has been a full pro- fessor at Kansai University. He received the Japan Petroleum Institute Award for Distinguished Papers in 1987, Divisional Award (Organic Synthesis) of the Chem- ical Society of Japan in 1999, Award of the Synthetic Organic Chemistry, Japan (Yu-uki Gosei Kagaku Kyokai) in 1999, and Award of the Japan Petroleum Insti- tute in 2002. His current research inter- ests include the development of practical oxidation reactions using molecular oxy- gen and hydrogen peroxide, homoge- neous , petrochemistry, organometallic chemistry directed towards organic synthesis.

Satoshi Sakaguchi was born in 1970 in Nishinomiya, Japan, completed his undergraduate study and graduate study for his master's degree at Kansai Univer- sity in 1993 and 1995, respectively. He joined Kansai University, Faculty of Engineering, as a assistant professor in 1995. He received his Ph.D. from Kansai University in 2001 under the direction of Professor Yasutaka Ishii. In 2003, he became a lecturer. His research interests are the development of catalytic func- tionalization reactions of hydrocarbons, and the development of new synthetic reactions using a transition metal com- plex as a catalyst.

1064 ( 24 ) J. Synth. Org. Chem., Jpn.