GRIGNARD ADDITION-REACTIONS TO 1,4-DIFUNCTIONALIZED BUT-2-YNES

Trisubstituted alkenes of E geometry have been prepared by anti additi on of Grignard reagents to 1,4-difunctionalized but-2-ynes. Addition o f primary, secondary and aromatic Grignard reagents to but-2-yne-1,4-d iol provided (E)-2-substituted but-2-ene-1,4-diols as major products a long with the corresponding 2-substituted buta-2,3-dien-1-ols. Additio n of phenylmagnesium bromide to the mono- and di-methyl ethers of but- 2-yne-1,4-diol gave 2,3-diphenyl-1,3-diene. Treatment of 4-dimethylami nobut-2-yn-1-ol with primary alkyl and alkenyl Grignard reagents affor ded the 2-substituted anti addition product regiospecifically, stereos pecifically and in high yield. Reaction of 1-dimethylamino-4-methoxybu t-2-yne with butylmagnesium bromide provided only the 3-substituted an ti addition product in good yield.