Carbonyl group with sodium borohydride

Condensation of piperazine with 2-methoxytropone gives the addition-elimination product 12 [2]. Alkylation of the remaining secondary amino group with bromoketone 13, itself the product from acylation of dimethyl catechol, gives aminoketone 14. Reduction of the carbonyl group with sodium borohydride leads to secondaiy alcohols 15 and 16. Resolution of these two enantiomers was achieved by recrystallization of their tartrate salts to give ciladopa (16) [3],... 

Leenheer et al. (1983) have recently shown that ketone functional groups can be determined by one of the following techniques (1) preparation of the methoxime followed by proton or C NMR spectroscopy of the derivative (2) reduction of the ketone carbonyl group with sodium borohydride followed by methylation of the resultant alcohol and NMR analysis of the methyl ethers. 

Michael addition to (+)-pu]egone [( + )-12] is not only possible with carbon nucleophiles, but also nitrogen and sulfur compounds. Thus, reaction of (+)-pulegone with benzylamine, followed by reduction of the carbonyl group with sodium borohydride, gives (1 / .3/ ,4,S )-8-(ben-zylamino)menthol (24)28, used for the formation of chiral 1.3-oxazines which react with Grignard reagents diastereoselectively (Section D. 1.3.1.4.). 

After reduction of the carbonyl group with sodium borohydride and protective silylation of the resulting hydroxy group, the auxiliary is removed by ozonolysis of the alkenylphos-phonamide group. By this method, or other obvious sequences, the primary products are converted into a series of enantiomerically pure, interestingly functionalized cyclopropane derivatives (Scheme 4), which should find applications as synthetic building blocks. 

Esterification of the ketoacid (39) with diazomethane afforded the ketoester (40). This, on treatment with sodium hydride and diethyl carbonate in 1,2-dimethoxyethane, furnished (41) whose NMR spectrum was rather complicated, probably due to contamination with a small amount of tautomer. Reduction of the free carbonyl group with sodium borohydride led to the formation of alcohol whose tosyl derivative on heating with lithium bromide and lithium carbonate in dimethylformamide gave the diester (42). Its spectroscopic properties were identical with those of the one reported [20]. As the diester (42) has already been converted to warburganal (12), the present route for the diester (42) constitutes a formal total synthesis of warburganal. 

The enzyme is a single enantiomer of a chiral molecule and binds the coenzyme and substrate m such a way that hydride is transferred exclusively to the face of the carbonyl group that leads to (5) (+) lactic acid Reduction of pyruvic acid m the absence of an enzyme however say with sodium borohydride also gives lactic acid but as a racemic mixture containing equal quantities of the R and S enantiomers... 

Acylation of 14 with cyclobutylcarbonyl chloride followed by the same series of transformations as above leads to intermediate 22. Reduction of the carbonyl group in that molecule with sodium borohydride gives the analgesic agonist/antagonist nalbuphine (23). 7... 

When 5,6-dihydro-l,3-thiazines 24 are treated with sodium borohydride, the carbonyl group is reduced to the alcohol 142 and the azomethine bond remains intact (Equation 8) <2000GHE862>. This is in contrast to 477-1,3-thiazines where the azomethine bond does react <1964JHC300>. 

---