Actylenic ketones

Reduction of acetylenic ketones, RC=CCR. Alpine-Borane can effect this reduction in high cnantioselcctivity, but this borane is very sensitive to steric effects. Thus it fails to reduce a carbonyl group adjacent to a /-butyl group. In contrast, asymmetric reduction of alkyl aryl ketones with I is increased by a hindered alkyl group. The same effect obtains in reduction of actylenic ketones (2). Thus as the steric bulk of R increases, the enantioselcctivity also increases. 

Reaction of the diacetonide of o-wannonolactone 208 with lithium acetylide gave the lactol of actylenic ketone, which with hydrazine was transformed into the pyrazole 209. This, upon acetolysis, gave 210... 

Methoxybenzenetellurinic acid anhydride, [/ -Me0C6H4Te(0)]20, catalyses the hydration of terminal actylenes to yield methyl ketones (equation 31)133. Unactivated alkynes 209 (Rl = H or alkyl, R = alkyl or Ph) are converted into ketones in refluxing aqueous... 

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