Olefins functionalizations, sodium borohydride

Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of tellurium powder with an aqueous ethanol solution of sodium borohydride, is an effective reducing reagent for many functionalities, such as azide, sulfoxide, disulfide, activated C=C bonds, nitroxide, and so forth. Water is a convenient solvent for these transformations.28 A variety of functional groups including aldehydes, ketones, olefins, nitroxides, and azides are also reduced by sodium hypophosphite buffer solution.29... 

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... 

Treatment of the reduced intermediate (23-6) with butyl hthium leads to the anion from the removal of a proton on the methylene group reaction of that with methyl acetate affords the methyl ketone (24-1), which contains two of the three required side chain carbon atoms. The additional carbon atom and the basic function are incorporated by means of a Mannich condensation. Thus, reaction of (24-1) with A-methylpiperazine and formaldehyde leads to the aminoketone (24-2). The carbonyl group is then reduced with sodium borohydride and the resulting alcohol is dehydrated by reaction with phosphoms oxychloride in pyridine. In this case, too, the Z isomer is responsible for most of the activity. This is isolated from the resulting mixture of olefins to afford thiothixene (24-3) [25]. 

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