Synthesis of 18,18-difluoro- or 18,18,18-trifluoro-3-methoxy-12-oxaestra-1,3,5(10)-trienes

Add time:10/01/2019    Source:sciencedirect.com

Titanium tetrachloride mediated dialkylation of acetic anhydride, trifluoroacetic anhydride or difluorochloroacetic anhydride by 1,8-bis(trimethylsilyl)-2,6-octadiene (BISTRO) leads, respectively, to dl-1-methyl-2,5-divinylcyclopentan-1-ol, dl-1-difluoromethyl-2,5-divinylcyclopentan-1-ol or dl-1-trifluoromethyl-2,5-divinylcyclopentan-1-ol. Esterification of these compounds with 4-methoxybenzocyclobutene-1-carboxylic acid and then pyrolysis led to 3-methoxy-12-oxa-17-vinylestra-1,3,5(10)-trien-11-one and to corresponding 18,18-difluoro or 18,18,18-trifluoro derivatives. Further transformations give rise to 3-methoxy-12-oxa-17-(2-oxoethyl)-18,18-difluoroestra-1,3,5(10)-trien-11-one and to the corresponding 18,18,18-trifluoro derivative.

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