ORGANOBORANES .31. A SIMPLE PREPARATION OF BORONIC ESTERS FROM ORGANO-LITHIUM REAGENTS AND SELECTED TRIALKOXYBORANES
ORGANOBORANES .31. A SIMPLE PREPARATION OF BORONIC ESTERS FROM ORGANO-LITHIUM REAGENTS AND SELECTED TRIALKOXYBORANES
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DOI：
10.1021/om50004a009
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发表时间：
1983-01-01
期刊：
影响因子：
2.8
通讯作者：
COLE, TE
中科院分区：
文献类型：
--
作者：
BROWN, HC;COLE, TE
The reaction of methyllithium with trimethoxyborane at-78 C in ethyl ether yields a mixture of methylated boranes and their corresponding “ate” complexes. We have found that under the same conditions triisopropoxyborane reacts cleanly with methyllithium to form the lithium methyltriisopropoxyborate complex. Protonationof this complex with anhydroushydrogen chloride quantitatively yields methyl diisopropoxyborane. This reaction of organolithium reagent with triisopropoxyborane appears to provide a general, valuable route to boronic esters. Other alkoxyboranes were examined for their selectivity for monomethylation by methyllithium. In addition to triisopropoxyborane, triisobutoxyborane and tri-sec-butoxyborane also give the methylboronic esters quantitatively. This development provides the first general preparation of boronic esters from organolithium reagents.The utility of boronic esters and acids has largely been limited in the past to protecting groups in carbohydrate chemistry1 11and as derivatizing agents for difunctional compounds for GC and GC-MS analysis. 2 Recently the homologation of boronic esters has been demonstrated, and this promises to become an important application of bo-ronic esters. 3-5 A variety of methodshave been used to prepare boronic esters. Theaddition of Grignard reagents to trialkoxyboranes at low temperatures followed by an
