NEW TOOLS IN SYNTHESIS 1055 Recent Advances of BINAP Chemistry in the Industrial Aspects Hidenori Kumobayashi, Takashi Miura,* Noboru Sayo, Takao Saito, Xiaoyong Zhang Central Research Laboratory, Takasago International Corporation, 1-4-11 Nishi-yawata, Hiratsuka, Kanagawa 254-0073, Japan Fax (0463)25-2084; E-mail: [email protected] Received 24 April 2001 and ketones such as a-(acylamino)acrylic acids,6 enam- Abstract: New efficient synthetic methods of optically active BI- 7 8 ides, a,b-unsaturated carboxylic acids, allylic and ho- NAP [BINAP = 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl] and 9 10 its variants are described. Application of these BINAP variants in moallylic alcohols, alkylidene lactones, alkenyl 10 11 12 asymmetric catalytic hydrogenation of prochiral ketones and olefins ethers, b-keto esters, b-hydroxyketones, and b-ami- to various industrially important compounds is discussed. noketones.12 Key words: BINAP ligands, ruthenium and iridium catalysts, Starting with the development of l-menthol process using asymmetric hydrogenation, ketones, unsaturated carboxylic acids BINAP–Rh catalyzed asymmetric isomerization of allyl- amines,5a we have been investigating catalytic asymmet- ric synthesis mainly based on BINAP chemistry for two Introduction decades and have developed various asymmetric synthet- ic processes. All of these results are based on the success Enantioselective syntheses have been gaining more and of the marvelous abilities of the BINAP ligands. Recently more importance in a wide range of fields such as pharma- the targets of asymmetric synthesis have become varied ceuticals, agrochemicals, food additives, aromachemicals and complicated, while BINAP sometimes shows its lim- and functional materials because the biological activities itation. It becomes necessary to develop new ligands to of these materials are often associated with their absolute compensate for the limitations of BINAP. In this paper we configuration. described recent developments of BINAP chemistry, es- pecially about syntheses and applications of new BINAP Known methods to obtain enantiomerically pure com- ligands from the industrial point of view. pounds are classified as follows: 1) optical resolution, 2) modification of naturally occurring materials, 3) biologi- cal transformation, and 4) asymmetric catalysis using a New Synthetic Methods of BINAP and Its Variants prochiral compound as the starting material. Among these methods, asymmetric catalysis is emerging as one of the Since the practical methods for synthesis of 2,2’-bis(dia- most efficient and versatile methods for the preparation of rylphosphino)-1,1’-binaphthyls (BINAPs) were reported a wide range of chiral target molecules. In recent years, in 1986,13 a series of BINAP analogues have been pre- numerous catalytic asymmetric reaction processes that pared. However, this route requires harsh conditions for transform prochiral substrates into chiral products with 1 the conversion of binaphthol to the corresponding dibro- high enantioselectivity have been developed. Asymmet- mide and tedious optical resolution of BINAP derivatives ric hydrogenation is one of the most powerful tools for the (Scheme 1). synthesis of enantiomerically pure compounds. For this purpose, several kinds of metal–optically active phos- Recently, Cai et al. of Merck developed a new method for phine complexes have been synthesized so far. In general, direct asymmetric synthesis of BINAP by use of nickel- catalyzed coupling reaction of easily accessible chiral a chiral transition metal catalyst precursor LnM can be re- garded as composed of two key parts, the chiral ligand L 2,2’-bis((trifluoromethanesulfonyl)oxy)-1,1’-binaphthyl and the central metal M. Thus, the proper combination of (1) with diphenylphosphine in the presence of DABCO 14 well-designed chiral ligands and selected metals is the (Scheme 2). Similarly, Laneman et al. of Monsanto re- most important requirement for high catalytic efficiency. ported the nickel-catalyzed cross-coupling of 1 with chlo- 15 Over the past twenty-five years, various kinds of chiral rodiphenylphosphine in the presence of zinc. These phosphines have been developed by researchers in methods, however, have some drawbacks in industrializa- academic, pharmaceutical and fine chemical companies. tion, such as use of pyrophoric diphenylphosphine or Among them, 2,2’-bis(diphenylphosphino)-1,1’- moisture-sensitive chlorodiphenylphosphine. binaphthyl2 (BINAP) has been found to have remarkable On the other hand, we have explored two unique proce- chiral recognition ability and broad applicability in vari- dures for the synthesis of chiral BINAPs by using the met- ous transition metal-catalyzed asymmetric reactions such al-catalyzed coupling reaction of 1 with diarylphosphine as hydrogenation,3 hydrosilylation,4 1,3-hydrogen migra- oxides, which are readily prepared by the reaction of aryl- tion,5 etc. For example, BINAP–ruthenium catalysts are magnesium halide with diethyl phosphite and easy to han- well recognized to be highly efficient catalysts for asym- dle in large quantity.16 The first one is well illustrated by metric hydrogenations of various functionalized olefins coupling of (R)-1 with diphenylphosphine oxide, which Synlett 2001, No. SI, 1055–1064 ISSN 0936-5214 © Thieme Stuttgart · New Yorkrt · New York 1056 H. Kumobayashi et al. NEW TOOLS IN SYNTHESIS Biographical Sketches Hidenori Kumobayashi thol with enantioselective cal Society of Japan Award was born in Niigata, Japan. isomerization of allylamines for Technical Development. In 1967 he obtained a B.S. catalyzed by BINAP—Rh(I) He is now a vice president at degree from Shinsyu Univer- complexes as the key reac- Takasago International Cor- sity and joined Takasago In- tion. This was followed by poration and the general ternational Corporation. In studies on efficient synthesis manager of Fine Chemical 1986 he earned his Ph. D. of key intermediates of car- Devision. His main research from Osaka University under bapenem antibiotics by using interests include asymmetric the direction of Prof. Sei Ot- BINAP—Ru(II)-catalyzed synthesis using transition suka where he worked on de- asymmetric hydrogenation metal catalysts. velopment of industrial of ketone compounds. In synthetic process of l-men- 1997 he received the Chemi- Takashi Miura obtained a nonium salts with Prof. Paul Central Research Laboratory Ph.D. from Tokyo Metropol- G. Gassman at University of of Takasago International itan University in 1979 under Minnesota from 1979 to Corporation. Like his collab- the guidance of Prof. Michio 1981. In 1982 he joined orator, he is convinced that Kobayashi. He pursued post- Takasago International Cor- asymmetric catalysis offers doctoral research on the 2,3- poration and is now general many attractive options for sigmatropic rearrangement manager at Fine & Aroma organic chemist and indus- of sulfonium salts and sele- Chemical Laboratory in try. Noboru Sayo, born in join the Professor Nakai’s re- Central Research Laboratory Hyogo, Japan, in 1954, stud- search group and worked in of Takasago International ied applied chemistry at the field of carbanion chem- Corporation. His main re- Shinsyu University, and ob- istry. After obtaining his search interests have been tained his M. S. degree in ap- Ph.D. in 1984, he entered associated with the develop- plied chemistry from Takasago International Cor- ment of catalytic asymmetric Okayama University in poration. Now he is assistant synthesis. 1979. He moved to Tokyo director at Fine & Aroma Institute of Technology to Chemical Laboratory in Takao Saito was born in his Ph. D. from Osaka Uni- of Takasago International Ibaraki (Japan) in 1960. He versity under supervision of Corporation. His current obtained his M.S. degree Prof. Shun-ichi Murahashi in area of research includes the from Meiji College of Phar- 1996 and is now research as- development of new molecu- macy in 1985 and then sociate at Fine & Aroma lar catalysts. joined Takasago Internation- Chemical Laboratory in al Corporation. He received Central Research Laboratory Xiaoyong Zhang was born University under supervision tory in Central Research in Zhejiang, China and re- of the late Prof. Hidemasa Laboratory. He is pursuing ceived his M.S. degree in or- Takaya in 1994 and then exploration of new efficient ganic chemistry at Institute joined Takasago Internation- synthetic methods of chiral of Chemistry, Chinese Acad- al Corporation where he is ligands and their application emy of Sciences in 1987. He now a senior chemist at Fine to asymmetric catalysis. earned his Ph.D. from Kyoto & Aroma Chemical Labora- Synlett 2001, No. SI, 1055–1064 ISSN 0936-5214 © Thieme Stuttgart · New York NEW TOOLS IN SYNTHESIS Recent Advances of BINAP Chemistry in the Industrial Aspects 1057 OH i)Br ii)MgBr iii) OH Br MgBr rac-Binaphthol rac-Dibromide iv—vi) vii) P(O)Ph2 P(O)Ph2 PPh2 P(O)Ph2 P(O)Ph2 PPh2 rac-BINAPO (R)-(+)-BINAPO (R)-(+)-BINAP - Scheme 1 i) Br2, PPh3, 230 °C; ii) Mg; iii) Ph2P(O)Cl; iv) (2R,3R)-( )-di-O-benzoyltartaric acid; v) fractional crystallization; vi) NaOH; vii) Cl3SiH, PhNMe2. toluene, giving (R)-BINAP in 96% yield. This procedure has been successfully applied to the synthesis of a series of known or new chiral BINAP ligands in reasonable to OTf a or b PPh 2 good yields. It is noteworthy that most of these new BI- OTf PPh 2 NAPs had been difficult to obtain through the optical res- olution route shown in Scheme 1. However, when (R)-2,2’-bis((trifluoromethanesulfo- (R)- or (S)-1 (R)- or (S)-BINAP nyl)oxy)-5,5’,6,6’,7,7’,8,8’-octahydro-1,1’-binaphtyl