A general method for the preparation of cumulenic ethers and thioethers

Abstract

Solutions of lithiated cumulenic ethers and bis-ethers R2CH=C=C=C(Li)OR3 and R10CH=C=C=C(Li)OR3 can be obtained by treatment of the compounds R10CH(R2)C=CCHz0R3 and R10CH2C=CCH(OR3)z respectively with 2 equivalents of butyllithium in ether. Reaction of these solutions with HzO, DzO, methyl iodide, a-chloroethers or ketones gives the cumulenic compounds or their derivatives in good yields.Solutions of lithiated cumulenic thioethers R2CH=C=C=C(Li)SR3 are obtained in an analogous way, but hydrolysis affords the isomeric enynic thioethers R2CH=CHC=CSR3 in addition to the expected curnulenic thioethers R2CH=C=C=CHSR3. Elimination of R'OH from R10C(R2)zC=CCH(SR3)2 with 1 equivalent of C4HgLi leads to the cumulenic dit hioacetals ( R Z ) K = C =C = C(SR3)2.

Synthesis of the Butatriene C4 Function: Methodology and Applications

“…Brandsma et al reported a quite general procedure for the preparation of butatrienyl ethers and thioethers by basic treatment of bispropargylic diethers or dithioethers containing a primary propargylic functional methylene groups (CH 2 X, X = O, S), followed by a trapping of the butatrienyllithium intermediates with electrophiles (Scheme ) . Butatrienyl ethers were thus obtained in quite good yields, while butatrienyl thioethers were generally obtained in mixture with their enynyl thioether isomers, probably arising from the hydrolysis of the enynyl form of the lithiated intermediates.…”