在本文中,我们报道了使用HI内炔的有效且实用的碘氢化生成易地从容易获得的三乙基硅烷和我2。该系统具有高区域选择性和立体选择性,可在温和条件下以良好的收率提供 ( E )-乙烯基碘化物。此外,氢碘化反应显示出对烷基、甲氧基、卤素、三氟甲基、氰基、酯、卤代甲基、酸敏感性甲硅烷基醚和缩醛部分的高官能团耐受性。
A silver-catalyzed carbomagnesiation of alkynes with alkyl halides and Grignardreagents afforded alkenyl Grignardreagentsregioselectively, where the alkyl group of the alkyl halide, but not that of the Grignardreagent, was introduced into the alkyne. Application to δ-haloalkylacetylenes yielded cyclopentanes or a tetrahydrofuran containing an exo-methylene substituent via 5-exo-dig cyclization
Treatment of terminal acetylenes (R1CCH) with secondary or tertiary alkyl iodides (R2I) in the presence of triethylborane provides the corresponding alkenyl iodides (R1C(I)CHR2) in good yields.
Iodine atom transfer addition reactions with alkynes. Part 1: Alkyl iodides
作者:Dennis P. Curran、Dooseop Kim
DOI:10.1016/s0040-4020(01)86550-9
日期:1991.8
Simple 2° - and 3° -alkyl iodides add smoothly to electron deficient alkynes under standard atom transfer conditions 10% Bu3SnSnBu3, sunlamp photolysis. Mechanistic experiments help to interpret stereochemical and yield trends, and a new model for atom abstraction reactions of rapidly inverting a-vinyl radicals is proposed.
Surface-Mediated Reactions. 4. Hydrohalogenation of Alkynes
作者:Paul J. Kropp、Scott D. Crawford
DOI:10.1021/jo00090a031
日期:1994.6
The use of appropriately prepared silica gel and alumina has been found to mediate the addition of hydrogen halides to alkynes. The technique has been rendered even more convenient by the use of various organic and inorganic acid halides that react in the presence of silica gel or alumina to generate hydrogen halides in situ. Treatment in this fashion of 1-propynylbenzene (1), which underwent no reaction in CH2Cl2 solution saturated with HCl, readily afforded the syn addition product, alkenyl chloride (E)-4a. On extended treatment (E)-4a underwent subsequent isomerization to the thermodynamically more stable Z isomer. Thus either isomer of 4a could be obtained in good yield depending on the reaction conditions. In a similar way bromides (E)- and (Z)-4b were obtained without competing formation of the radical products (E)- and (Z)-5, which occurred in solution. In contrast with solution-phase hydriodination of alkyne 1, which slowly afforded iodide (E)-4c, surface-mediated addition readily afforded (E)-4c, followed by isomerization to the Z isomer. E reversible arrow Z equilibration of the alkenyl halides 4 was shown to involve, at least in part, addition-elimination via the gem-dihalides 13. Analogous behavior was exhibited by the phenylalkynes 2 and 3 on surface-mediated hydrohalogenation. Surface-mediated addition of Hbr and HI to the internal alkylalkyne 14 afforded principally the anti addition products (Z)-15b,c. Treatment of the terminal alkynes 17 and 22 with (COBr)(2) over alumina gave the dibromides 20 and 24/25,respectively, whereas use of acetyl bromide as the Hbr precursor afforded the alkenyl bromides 18b and 23.
Homolytic allylation of vinyl iodides with allylstananes
In the presence of AIBN or Et3B, a variety of vinyl iodides reacted with allylstannanes bearing an electron-withdrawing group at the beta-position to afford 1,4-dienes in moderate to good yields. The allylation showed high stereoselectivity when the alpha-substituent of the iodides was a phenyl group, or the B-substituent was a bulky group. (C) 1999 Elsevier Science Ltd. All rights reserved.