Ketone reduction with sodium borohydride

Reduction Carbonyl groups in carbohydrates are reduced by the same methods used for aldehydes and ketones reduction with sodium borohydride or lithium aluminum hydride or by catalytic hydrogenation. 

Reduction to alcohols (Section 15 2) Aide hydes are reduced to primary alcohols and ketones are reduced to secondary alcohols by a variety of reducing agents Catalytic hydrogenation over a metal catalyst and reduction with sodium borohydride or lithium aluminum hydride are general methods... 

In a similar vein, acylation of the corticoid 50 with furoyl chloride gives the diacyl derivative 51. Reduction with sodium borohydride serves to convert the 11-ketone to the alcohol 52. Hydrolysis under mild acid conditions preferentially removes the acyl group at the less hindered 21 position. The hydroxyl group in that derivative (53) is then converted to the mesylate 54. Replacement by chlorine affords mometasone (55) [12]. 

Traynelis et al. described the preparation of 4-chlorobenzo[6]thiepin (24) via the key intermediate, 7a-chlorocyclopropa[6]benzo[6]thiapyran-7-one (25fK The ketone 25 underwent reduction with sodium borohydride to give the corresponding alcohol, which was ring opened with hydrochloric acid to yield the precursor 26 of... 

The reduction of ketones containing nitro groups to nitro alcohols is best carried out by borohydrides. 5-Nitro-2-pentanone was converted to 5-nitro-2-pentanol in 86.6% yield by reduction with sodium borohydride at 20-25°. Other nitro ketones gave 48.5-98.7% yields, usually higher than were obtained by Meerwein-Ponruiorf reduction [907]. 2-Acetamido-3-(p-nitrophenyl)-l-hydroxypropan-3-one was reduced with calcium borohydride at — 30° to 70% of threo- and 10% of er7tAro-2-acetamido-3-(p-nitrophenyl)propane-l,3-diol while sodium borohydride afforded a mixture of the above isomers in 25% and 47% yields, respectively [902]. 

The CD fragment 1s synthesized starting with resolved bicyclic acid 129. Sequential catalytic hydrogenation and reduction with sodium borohydride leads to the reduced hydroxy acid 1. The carboxylic acid function is then converted to the methyl ketone by treatment with methyl-lithium and the alcohol is converted to the mesylate. Elimination of the latter group with base leads to the conjugated olefin 133. Catalytic reduction followed by equilibration of the ketone in base leads to the saturated methyl ketone 134. Treatment of that intermediate with peracid leads to scission of the ketone by Bayer Villiger reaction to afford acetate 135. The t-butyl protecting... 

Enamidines (2). Lithiation of 1 followed by treatment with aldehydes or ketones results in Peterson olefination to give a mixture of isomeric enamidines (2) in good yield. These enamidines can be used to convert the carbonyl compounds used in (heir preparation to homologated amines, aldehydes, and ketones. Conversion to a mclhylaminc involves reduction with sodium borohydride (pH 6) to an aminal, which is then hydrolyzed by dilute acid. The sequence can be carried out from 1 without isolation of any intermediates (equation I). 

The quaternary salts of ketals of 4-pyridyl alkyl and aryl ketones undergo reduction with sodium borohydride to give the expected 1,2,3,6-tetrahydropyridines.47" Reduction of an analogous ketal of a quaternary salt of a 3-pyridyl ketone led to rupture of the ketal ring.476... 

The 7-hydroxy telluride 161 is prepared by hydrotelluration of methyl vinyl ketone, followed by in situ reduction with sodium borohydride.154 Treatment of 161 with 2 equiv. of nBuLi, followed by capture of the dianion 162 with electrophiles, gives the corresponding alcohols 163.252 Dianions like 162 can be transmetallated with CeCf , leading to organometallics of the type 164, which on reaction with lactones give spiroketals (Scheme 94).253... 

Other examples are also reported. ft32% erythro, 8% threo By reduction with sodium borohydride in situ. "Sequential reaction with organomagnesium or organolithium compounds used to prepare unsymmetrical ketones [17]. 

The ring expansion of the benzoxepinones 134 to benzoxocinones 136 involved a cyclopropanation with diazomethane in the presence of palladium acetate and a catalytic hydrogenation. The cleavage of the more labile internal bond in the cyclopropyl derivatives 135 leads to the eight-membered ketones 136 exclusively in excellent yields (90-95%). Reduction of ketones 136 with sodium borohydride affords the hydroxy derivatives 137 in a stereo-controlled manner (Scheme 34) <2002CC634>. 

The diazepinol (40) is readily obtained from ketone (10) with sodium borohydride and is converted back into 10 with A -bromoacetamide or by Oppenauer oxidation.32 In a similar manner 32 and the AT-acetyl derivative of 10 can be reduced to carbinols. Acylation of 40 or treatment of the reduction product of 32 with acetic acid gave the trans-annular oxide (41). The carbinol (40), the acetyl carbinol from 10, the oxide (41), and the diacetyl analog of 41 all undergo rearrangement with mineral acid to give the four furfurylhydrazines (42).32... 

Homocyclic ketones 290 (X = CH2) and 291 predominantly undergo a type B attack, although the reduction with sodium borohydride increases the amount of the minor A isomer. Attack from the A side prevails slightly only in the 6-phenyl-substitutcd Mannich base 290 (X = CH,. R = Ph). ... 

A ketone added to the aged solution is reduced effectively, but a carboxylic acid or ester is not reduced. This weak hydride donor is thus useful for the selective reduction of a keto acid to the corresponding hydroxy acid. Both intermolecular 2md intramolecular competition experiments with tetrakis-(N-dihydropyridyl)-aluminate showed that diaryl ketones are more reactive to this reagent than either dialkyl or aralkyl ketones. This relationship is the opposite of that found by H. C. Brown for reduction with sodium borohydride in isopropyl alcohol, where the order of reactivity is acetone > acetophenone > benzophenone. 

Tamm found the reagent useful for reduction of carbonyl groups in the bufadien-olide series. Thus reduction of the ketone (11) with sodium borohydride suffered from the fact that the unsaturated lactone ring is attacked to some extent and the yield of (12) was only 40-50%. Reduction with lithium tri-f-butoxyaluminum hydride in tetrahydrofurane at 0° proceeded rapidly (15 min.), the lactone ring was... 

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