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Reactions of Alkylmercuric Halides with Sodium Borohydride in The

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870 Reactionsof Alkylmercuric Halides with Sodium Borohydride in the Presenceof Molecular Oxygen' Craig L. Hill and George M.Whitesides* Contribution from the Department of Chemistry, Massachusetts Institute of Technolog)', Cambridge, Massochusetts 02 I 39. ReceiuedAugust 24, 1973 Abstract: Reaction of alkylmercuric halides with sodium borohydride in dimethylformamide saturated with molecular oxygen producesalcohols and borate estersin good yields. The products obtained following reaction of neophylmercuric bromide (l), 1,7,7-trimethylbicyclol2.2.llheptyl-2-mercuricbromide (9), and endo- and exo-nor- bornyl-2-mercuric bromides (13 and l4) with borohydride in the presenceof oxygen are compatible with a reaction mechanism involving free, noncaged,alkyl radicals as intermediates. This mechanism finds further support in the observationsthat rcaction of I with borohydride and oxygen in solutions containing2,2,6,6-tetramethylpiperidoxyl radical leads to good yields of thc prodr-rctof coupling of neophyl radical with the nitroxyl. Reaction of a-alkoxyl alkylmercuric halides with borohydridc and oxygen generatcsa-alkoxyl alcohols in good yields; similar reaction of a-hydroxy alkylmercuric halides doesnot lead to vicinal diols. [lkyl radicalsare establishedintermediates in the re- synthesis, provided that these alkyl radicals survive 11 ductiveclemercuration of alkylmercurichalides by sufficientlylong to be accessibleto reagentspresent in metal hydrides.2-a The loss of stereochemistrythat their solutions. One previous attempt to trap alkyl occursduring conversionof the carbon-mercury bonds radicals produced during reductive demercurationlead of diastereomeric2-norbornylmercury compounds into to ambigllous rr-sults: reaction of 2-norbornylmer- carbon-hydrogen bonds, the characteristic structural curic bronride with sodium borohydride in the pres- rearrangementsthat accompany demcrcuration of ence of high concentrations of di-tert-butylnitroxyl nortricyclyhnercurycompounds, and the absenceof l,- (DTBNO) produced approximately 20% of N,lf-di- 2-phcnyl migration on reduction of neophylmercuric tert-bntyl-O-2-norbornylhydroxylarnine.2 This yield is bromide combine to define the lifetimesof the inter- lower than that expectedfor reaction between free 2- rnediatealkyl radicalsin thesereactions to be short, norbornyl radicalsand DTBNO by analogywith other br"rtdo not diffcrcntiate between radical-cage mech- reactions involving this or similar scavengers,T'8but anisms(of which onc possiblesequence is reprcscnted steric hindrance may contribute to the apparent ineffi- by eq 2 and 3) and rapid radical-chain reactions (eq ciency of the coupling reaction in this instance. This 4 and 5). paper describesexperiments intended to establishcon- ditions under which alkyl radicals, generated from ]I}I RHgBr --> RHgH (l) alkylmercuric halides by reaction with sodium boro- hydride, can be diverted from the normal path leading --> .HgH (2) RHgH R. + to hydrocarbon by an external reagent. Molecular R' + 'HgH ---> RH * Hg(O) (3) oxygen was chosenas radical scavengerin theseexperi- it is highly reactivetoward RHgH---> R. (-1t mentsfor severalreasons: alkyl radicalsl'but relativelyunreactive toward organo- -> (s) R' + RHgH RH + R. + Hg(O) mercurycompoundst' and borohydrideion; it has small ancl its successfulcoupling with Since alkylrncrcuric halides are among the most steric requirements: moieties derived from organomercury reagents, readily availableand most tractableof organometallic alkyl particularly those synthesized by oxymercuration, compounds,;'';and sincetheir reductivedemercuration provide Lrseflllnew methods of forming carbon- is a particularly facile process,the reaction of alkyl- wor-rld and of adding functionality to olefinic mercurichalides with rnetalhydridcs seems potentially oxygen bonds These experimentswere also intended to attractiveas a method of-generating alkyl radicalsboth rnoieties. help to diflerentiate between the two types of mech- for mechanisticstudics and for nossiLrleutilization in anistic schemesoutlined by eq 2-5, by qualitatively (l) Supportedby tlre NationalInstitutes of Hcalth, Grants No. GM- establishingthe rapidity with which the generationand 16020ancl HL-15029, ancl by' thc National ScierrceF'ounclation, Crant No. GP-28-5E6X. (7) J. R. Thorlas and C. A. Tolman, J. Amer. Chem.Soc.,84,2930 (2) G. M. Whitcsidesand J. San Filippo, Jr.,J. Antcr.Chem. 9oc.,92, (1962): S. F. Nelsortand P. D. Bartlett,ibid.,88,143 (1966). 661I ( 1970). (8) Butyl radicals.gencratcd by reactionof rr-butyl(tri-n-butylphos- (3) G. A. Gray ancl W. R. Jackson,.1. Anter. Clrem.Soc., 91, 6205 phinc)silver(I)rvith 2,2,6,6-tetramcthylpiperidoxyl(TMPO), are scav- (1969);D. J. PastoanclJ. Gont'trz, ibid.,9l,7l9 (1969). engeclalrnost quantitativclyby this nitroryl radical in ether solution (4) Recluctionlrsing othcr rcagcntsmay take an trnrelatedcoursc: when [BuAgPBu,r]o: 0.05 M and [TMPO]o : 0.05 M: P. E. I{cndall, c/. F. R. Jensen,J. J. Miller, S. J. Cristol, and R. S. Beckley, J. Org. D. E. Bcrgbrciter,and G. M. Whitesidcs,unpublished work. Butyl Chern.,37, 4341(1912). radicals producedby photolysisof cli-n-butylbis(triphcnylphosphine)- (5) L. G. Makarova arrclA. N. Ncsrncyanov,"Methods of Ele- platinr-rrrr(II)are scavengcdwith high elicicncy by DTBNO: G. M. rrrcrtto-OrganicChcnristry," Vol. 4, North-Hollancl Publishing Co., Whitcsides,J. F. Gaasch,and E. R. Stedronsky,"/. Amer. Chent.Soc., Arrsterdam, 1967: t.. G. Makarova, "Organomctallic Reactiorrs," 94. 5258(972). Vol. 1, E. I.Bc'ckcr ancl M. Tsr-rtsui,Ed., Wiley-Interscier.lce,Ncw (9) Thc rate constantsfor rcaction of alkyl radicals rvith oxygen are York, N. Y., 1970,p I l9 ff'; Vol. 2, p 335ff. >107 l. mol-r scc 1: c/. B. Smaller,J. R. Remko, and E. C. Avery, (6) W, Kitching,Orgunometal. Chem. Rea.,3,35 (1968); W. Kitch- J. Chetrt.Phys.,48, 5174 (1968); A. A. Miller and F. R. Mayo, ./' ing in "OrganometallicReactions," Voi. 3, E. L Bcckerand M. Tsutsui. Amer. Chettt.Soc.,78,1017 (1956); C. M. Bamford and M. J. S' De- Ed., Wiley-Intersciencc,New York, N.Y., 1972,p319 tr. war, Proc. Roy. Soc.,Ser. A, 198,252(1949). [Reprinted from the Journal of the American Chemical Society, 96,870 (1974).] Copyright I974by the American Chemical Society and reprinted by permission of the copyright owner. 871 CHz --QHr (QFgnc'zo* ,r@g;n*.*-"3 @*,h:,9Hs I t-u o ( J @[1.1-. q I o --@[5,. J tt3 lrl ; ADDITION TIME ( min ) Figure 1. Product yields from reaction of neophylmercuric bromide (1) with sodium borohydride in the presenceof oxygen as a function of the addition rate of l0 ml of a 0.05 M solution of 1 to a O.23M solution of borohydride in dimethylformamide: (t) yields of neophyl alcohol (2); (o) yields of benzyldimethylcarbinol (3); and (A) yields of tert-bulylbenzene. Oxidations were carried out using 0.5 mmol of L and 0.7 mmol of sodium borohydride. r --] / r -'l Lwq)/ [RHqBrJ consumption of radical intermediates in reductive demercurationoccurs. Figure 2. Product yields for reaction of neophylmercuric bromide (1) and trcrns-2-methoxycyclohexylmercuricbromide (5) with sodium Results borohydride in the presenceofoxygen, as a lunction ofborohydride. Yields of products are representedby: (n) neophyl alcohol (2); Products. Initial experiments establishedthat the (O) benzyldirnethl'lcarbinol (3); (A) tert-butylbenzene(4); (rt reaction of alkylmercuric halides with sodium boro- Iruns-2-methoxycyclohexanol (6) ; (o) cis-2-methoxycyclohexanol hydride in dimethylformamidesolution in the presence (17): (l) cyclohexylmethyl ether (8). of molecular oxygen does yield alcohols as significant products. Using similar reaction conditions, the organomercurycompounds were sensiblyinert to oxy- CH, I xatltlr,o: gen in the absenceof'borohydride ion. The mercury- Ph-C-CHrHg Br ---------> (II) originally presentin the organomercuryreagent is I t)\rF' reducedto mercury(O)in high yield during reduction in CHt the presenceof oxygen,as it is during reductionsin the I absenceof oxygen. CH.' CHa CHt I part I I I The reaction conditionsused in the major of the ph-c= cH,roH + PhcH,-c-oH + Ph-c-cH3 (6) work reported in this paper are basedon the resultsof rll investigationsof the influenceof solvent,order and rate CHI CH' CH, 234 of addition of reagents,and work-up procedureon the 77i;$s\) 8%$%) 3%(377) yield of these alcohols. A number of dipolar aprotic solvents both dissolved and were chemically inert to yields shown without parenthesesin eq 6 are those ob- sodiumborohydride and alkylmercurichalides: DMF tained by glpc analysisof the reaction mixture without rather than dimethyl sulfoxide or hexamethylphos- work-up imrnediately after addition of the alkylmer- phoramide was selectedfor use on the basisof cost and curic halide had been completed; the yields in paren- convenienccof purification and removal in work-up. theseswere obtained by glpc analysisafter hydrolysisof Reactions were carried out by adding a solution of the reaction mixture (oide infra). Only the forn-rerare alkylmercurichalide in DMF at room temperatureto a reproduced in Figure 1. For the concentrationsand solutionof sodium borohydridein DMF through which quantities of reagents typically used in these experi- a stream of oxygen was passedrapidly; comparable ments ([RHgBr]s : 0.05 M (0.5 mmol), [NaBHrio : results were obtained by adding a solution of sodium 0.23 M (0.7 mmol)) the yields of alcoholsdid not in- borohydride to an oxygen-saturatedsolution of organo- creaseif addition of the alkylmercuric halide was car- mercury compounds. The rate of addition of the so-
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    inorganics Review A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review Liuzhang Ouyang 1,2,3, Hao Zhong 1,2, Hai-Wen Li 4,* ID and Min Zhu 1,2,* 1 School of Materials Science and Engineering, Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641, China; [email protected] (L.O.); [email protected] (H.Z.) 2 China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641, China 3 Key Laboratory for Fuel Cell Technology in Guangdong Province, Guangzhou 510641, China 4 Kyushu University Platform of Inter/Transdisciplinary Energy Research, International Research Center for Hydrogen Energy and International Institute for Carbon-Neutral Energy, Kyushu University, Fukuoka 819-0395, Japan * Correspondence: [email protected] (H.-W.L.); [email protected] (M.Z.) Received: 24 October 2017; Accepted: 5 January 2018; Published: 6 January 2018 Abstract: NaBH4 hydrolysis can generate pure hydrogen on demand at room temperature, but suffers from the difficult regeneration for practical application. In this work, we overview the state-of-the-art progress on the regeneration of NaBH4 from anhydrous or hydrated NaBO2 that is a byproduct of NaBH4 hydrolysis. The anhydrous NaBO2 can be regenerated effectively by MgH2, whereas the production of MgH2 from Mg requires high temperature to overcome the sluggish hydrogenation kinetics. Compared to that of anhydrous NaBO2, using the direct hydrolysis byproduct of hydrated NaBO2 as the starting material for regeneration exhibits significant advantages, i.e., omission of the high-temperature drying process to produce anhydrous NaBO2 and the water included can react with chemicals like Mg or Mg2Si to provide hydrogen.
  • United States Patent (19) 11 Patent Number: 5,847,110 Dragsten Et Al

    United States Patent (19) 11 Patent Number: 5,847,110 Dragsten Et Al

    USOO584711 OA United States Patent (19) 11 Patent Number: 5,847,110 Dragsten et al. (45) Date of Patent: Dec. 8, 1998 54 METHOD OF REDUCING ASCHIFF BASE 4,217,338 8/1980 Ouash ......................................... 424/1 4,419,444 12/1983 Quash ......................................... 435/7 (75) Inventors: Paul R. Dragsten, Chanhassen; 4,699.784 10/1987 Shih et al. ..... ... 424/85 Gregory J. Hansen, Fridley, both of 4,975,533 12/1990 Kondo et al. ... ... 536/55.3 Minn. 5,057,313 10/1991 Shih et al. ........................... 424/85.91 73 Assignee: Biomedical Frontiers, Inc., Minneapolis, Minn. OTHER PUBLICATIONS 21 Appl. No.: 911,991 Pelter, A. et al., “Reductive Aminations of Ketones and 1-1. Aldehydes using Borane-Pyridine”, J. Chem. Soc., Perkins 22 Filed: Aug. 15, 1997 Trans. 1, pp. 717–720 (1984). 51 Int. Cl. ........................... C08B 30/00; CO8B 37/00; C08B 37/02; CO7C 209/00 52 U.S. Cl. ........................ 536,124. 536/179536/185. Primary Examiner Howard C. Lee 536/18.7; 536/102; 536/112; 536/123.1; Attorney, Agent, Or Firm-Merchant, Gould, Smith, Edell, 564/123; 564/488; 564/489 Welter & Schmidt, PA. 58 Field of Search .................................. 536/17.9, 18.5, 536/18.7, 102, 112, 123.1, 124; 564/8, 57 ABSTRACT 123,489, 488 The invention relates to methods of reducing Schiff bases 56) References Cited and making chelator conjugates by treating with borane pyridine complex. U.S. PATENT DOCUMENTS 3,706,633 12/1972 Katchalski et al. ....................... 195/63 47 Claims, No Drawings 5,847,110 1 2 METHOD OF REDUCING ASCHIFF BASE includes Steps of reacting a water Soluble carrier with an amine, and treating reacted water Soluble carrier with BACKGROUND OF THE INVENTION borane-pyridine complex.