Synthesis of Ethylenes with Acyclic Quaternary Carbons by Dehydration of Neopentyl Alcohols. Application of the 2-D INAPT Technique

Article abstract of DOI:10.1021/jo00254a026

Di- and triquaternary ethylenes (5, 12 and 7, 19, Scheme I) have been synthesized by dehydration of sec- and tert-neopentyl alcohols (4, 11 and 6, 18) without rearrangement.It is thought that steric factors determine the structures of the products.The intermediate imines 2 and 14, from the reaction of nitriles 1 and 13 with t-C4H9Li, may be hydrolyzed only in the first case to ketones (3).More highly substituted ketones (10 and 16) were obtained by the reaction of t-RMgX (9) or (CH3)3CMgCl with 3,3-dialkyl and 2,3,3-trialkyl acid chlorides (8 and 15).Ketones 3 and 10 were reduced by LiAlH4 to secondary carbinols 4 and 11.The tertiary carbinols 6 were prepared from 3 by treatment with t-C4H9Li.The more hindered ketones 16 failed to add t-C4H9Li, but were reduced to secondary alcohols 18, instead of the desired tertiary alcohols 17.The carbinols 4, 6, 11, and 18 were dehydrated by heating with KHSO4.The 2-D INAPT NMR technique was used to establish the stereostructure of 19 by measuring the long-range heteronuclear coupling constants about the ene.