Heck Reaction of Protected Alk-1-en-3-ol, -4-ols, -5-ol or -6-ol with Aryl Bromides Catalysed by a Palladium Complex Derived from a Tetraphosphine
作者:Henri Doucet、Maurice Santelli、Florian Berthiol
DOI:10.1055/s-2006-926428
日期:2006.5
The tetraphosphine cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane in combination with [Pd(C3H5)Cl]2 affords a very efficient catalyst for the Heck reaction of protected alk-1-en-3-ols, -4-ols, -5-ols or -6-ols with aryl bromides. With 3-benzyloxyhex-1-ene or 4-benzyloxypent-1-ene, the (E)-1-aryl-3-benzyloxyhex-1-ene or (E)-1-aryl-4-benzyloxypent-1-ene derivatives were regio- and stereoselectively obtained. The protected ethylenic primary alcohols 4-benzyloxybut-1-ene, 4-tetrahydropyranyloxybut-1-ene, 5-tetrahydropyranyloxypent-1-ene and 6-tetrahydropyranyloxyhex-1-ene led in general to the (E)-1-aryl-4-benzyloxybut-1-ene or (E)-1-aryltetrahydropyranyloxyalk-1-enes as major isomers. However, with these substrates, the migration of the double bond was observed, and mixtures of isomers were obtained in most cases. The selectivities of the reactions depend both on electronic and steric factors. With electron-poor aryl bromides higher selectivities in favour of 1-arylalk-1-enol derivatives were generally obtained than with electron-rich aryl bromides. In the presence of sterically congested aryl bromides, larger amounts of products resulting from the migration of the double bond were observed. For example from 2,4,6-triisopropylbromobenzene and 6-tetrahydropyranyloxyhex-1-ene, 6-(2,4,6-triisopropylphenyl)hexanal was obtained as major product after deprotection. For most of these reactions, similar reactions-rates were observed with electron-poor and electron-rich aryl bromides. Several reactions can be performed with as little as 0.1% catalyst.
顺式、顺式、顺式-1,2,3,4-四(二苯基膦甲基)环戊烷四膦与 [Pd(C3H5)Cl]2 结合使用,是一种非常高效的催化剂,可用于受保护的烷-1-烯-3-醇、-4-醇、-5-醇或-6-醇与芳基溴化物的赫克反应。通过 3-苄氧基己-1-烯或 4-苄氧基戊-1-烯,可以获得 (E)-1- 芳基-3-苄氧基己-1-烯或 (E)-1- 芳基-4-苄氧基戊-1-烯衍生物的区域和立体选择性。受保护的乙烯基伯醇 4-苄氧基丁-1-烯、4-四氢吡喃氧基丁-1-烯、5-四氢吡喃氧基戊-1-烯和 6-四氢吡喃氧基己-1-烯的主要异构体一般是(E)-1-芳基-4-苄氧基丁-1-烯或(E)-1-芳基四氢吡喃氧基烷-1-烯。然而,在使用这些底物时,观察到了双键的迁移,在大多数情况下得到的是异构体的混合物。反应的选择性取决于电子和立体因素。与电子丰富的芳基溴化物相比,电子贫乏的芳基溴化物对 1-芳基烷-1-烯醇衍生物的选择性更高。在存在立体拥挤的芳基溴化物的情况下,由于双键迁移而产生的产物量更大。例如,从 2,4,6-三异丙基溴苯和 6-四氢吡喃氧基己-1-烯中,脱保护后的主要产物是 6-(2,4,6-三异丙基苯基)己醛。在大多数反应中,贫电子和富电子芳基溴的反应速率相似。一些反应只需 0.1% 的催化剂即可完成。