Ethynylcarbinol acetates

Synthesis of pregnane and corlieaid side chainsJ The l7 -ethynylcarbinol acetate (I) is reduced by zinc dust in refluxing diglyme, a process which is accompanied by rearrangement and elimination, to give the allenyl steroid (2) in 86% yield. The desired cortieoid side chain (3) can be formed from (2) by reaction with osmium tetroxide... 

The reagent reacts with ethynylcarbinol acetates to give alkylallenes.7 Sin-acetylenes are not transformed by (CH3)2CuLi into allenes. 

AlkylaUenes. Full details of the synthesis of alkylallenes from ethynylcarbinol acetates with organocopper reagents (2,152, ref. 7) have been published P. Rona and P. Crabbe,/1/n. Soc.,91,3289 (1969). 

Jacques developed a method for the hydration of a triple bond under nonacidic conditions for application to a series of steroid ethynylcarbinols, some of which are acid-sensitive. A suspension of 2 g. of mercuric acetate in a solution of 1 g. of I in... 

Rearrangement. Newman"" used Dowex-50 to rearrange ethynylcarbinols to a,/3-unsaturated ketones. For example, a mixture of 1-ethynylcyclohexanol, acetic acid, water, and the resin is refluxed for 45 mins. 

Rearrangement. Benn2 used silver perchlorate in refluxing acetone to rearrange the acetate of the ethynylcarbinol (4) to the isomeric allenes (5 and 6). Configurations were assigned on the basis of optical rotatory dispersion and NMR spectra. 

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