Chemistry of acetylenic ethers 82: On the different influence of alkylthio and alkoxy groups on the course of 1,4‐Eliminations

Abstract 1,4‐Elimination of alkanethiols RSH from the bis‐thioethers RSCH2CCC;H2SR with sodium ethoxide in liquid ammonia at −33°, affords two products viz. enynyl thioethers CH2CHC≡CSR and dienyl‐bis‐thioethers CH2CH‐C(SR)CHSR resulting from readdition of thiolate. Experimental evidence for the occurrence of cumulenyl thioethers CH2CCCHSR as intermediates in these elimination reactions is described. Reaction of the “mixed” compounds RSCH2C≡CCH2OR′, RSCH2C≡CCH(CH3)OR′ and RSCH2C≡C‐C(CH3)2OR′ with sodium ethoxide at −33° in liquid ammonia results in an elimination of the OR′ [R′ = alkyl or ‐CH(CH3)OC2H5] group and formation respectively of the enynyl thioethers RSC≡CCHCH2, RSC≡CCHCHCH3 and a mixture of RSC≡CCHC(CH3)2 and the carbinol RSCH≡C(OH)(CH3)] = CCH–C The carbinol can also be obtained by reaction of RSCHCCHC(CH3) = CH2 with lithium amide and acetaldehyde.