求助：NaBH4与醇类反应吗? chemie说的nabh4挺对的，补充一些资料 原文来源于encyclopedia of reagents for organic synthesis 关于nabh4的部分 solubility: sol h2o (stable at ph 14, rapidly decomposes at neutral or acidic ph); sol meoh (13 g/100 ml)1b, and etoh (3.16 g/100ml),1b but decomposes to borates; sol polyethylene glycol (peg),2a sol and stable in i-proh (0.37 g/100 ml)3 and diglyme (5.15 g/100 ml);1b insol ether;1b slightly sol thf.1c ethanol and methanol are usually employed as solvents, the former having the advantage of permitting reductions in homogeneous solutions with relatively little loss of reagent through the side reaction with the solvent.1aaprotic solvents such as diglyme greatly decrease the reaction rates.1a on the other hand, nabh4 in polyethyleneglycol (peg) shows a reactivity similar to that observed in etoh.2a although the full details of the mechanism of ketone reduction by nabh4 remain to be established,6 it has been demonstrated that all four hydrogen atoms can be transferred. moreover, the rate of reduction was shown to slightly increase when the hydrogens on boron are replaced by alkoxy groups.1a,c,d however, especially when nabh4 is used in meoh, an excess of reagent has to be used in order to circumvent the competitive borate formation by reaction with the solvent. ketone reduction has been accelerated under phase-transfer conditions7 or in the presence of hmpa supported on a polystyrene-type resin.8 the isolation of products is usually accomplished by diluting the reaction mixture with water, making it slightly acidic to destroy any excess hydride, and then extracting the organic product from the aqueous solution containing boric acid and its salts. 1. (a) brown, h. c.; krishnamurthy, s. t 1979, 35, 567. (b) ff 1967, 1, 1049. (c) seyden-penne, j. reductions by the alumino- and borohydrides in organic synthesis; vch-lavoisier: paris, 1991. (d) cos 1991, 8, chapters 1.1, 1.2,1.7, 1.10, 1.11, 1.14, 2.1, 2.3, 3.3, 3.5, 4.1, 4.4, 4.7. 2. (a) santaniello, e.; fiecchi, a.; manzocchi, a.; ferraboschi, p. joc 1983, 48, 3074. (b) santaniello, e.;ferraboschi, p.; fiecchi, a.; grisenti, p.; manzocchi, a. joc 1987, 52, 671. 3. brown, h. c.; mead, e. j.; subba rao, b. c. jacs 1955, 77, 6209. 4. stockmayer, w. h.; rice, d. w.; stephenson, c. c. jacs 1955, 77, 1980. 5. the sigma-aldrich library of chemical safety data, sigma-aldrich: milwaukee, 1988. 6. wigfield, d. c. t 1979, 35, 449. 7. bunton, c. a.; robinson, l.; stam, m. f. tl 1971, 121. subba rao, y. v.; choudary, b. m. sc 1992, 22, 2711. 8. tomoi, m.; hasegawa, t.; ikeda, m.; kakiuchi, h. bcj 1979, 52, 1653. [此贴子已经被作者于2004-7-5 21:10:00编辑过] 查看更多
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