4443-43-0Relevant academic research and scientific papers
Organoboranes. 56. Systematic study of the reactions of 1-alkenylboronic esters with representative organolithium and grignard reagents to provide an efficient, selective synthesis of organyl-1-alkenylborinic esters
Brown, Herbert C.,Vasumathi, Nagarajan,Joshi, Navalkishore N.
, p. 1058 - 1067 (2008/10/08)
A selective reaction of the ate complexes formed with 1-alkenylboronic esters and organolithium or Grignard reagents, by treatment with either Br?nsted or Lewis acids at -78 °C to give the corresponding organylalkenylborinic esters, is explored in this study. This systematic, detailed study reveals that the nature of the alkoxy group on boron, the nature and the amount of the alkyllithium or Grignard reagent used, the solvent, the reaction temperature, and the nature and amount of the acid used all play significant roles in influencing both the yield and the selectivity achieved for the formation of the desired organylalkenylborinates. Optimized procedures for the syntheses of representative organylalkenylborinic esters in high yield are summarized.
Organoboranes. 40. A simple preparation of borinic esters from organolithium reagents and selected boronic esters
Brown, Herbert C.,Cole, Thomas E.,Srebnik, Morris
, p. 1788 - 1792 (2008/10/08)
Monoorganyldiisopropoxyboranes, RB(O-i-Pr)2, react cleanly at -78 °C with 1 equiv of organolithium compounds, R′Li, to form the corresponding complexes of the borinic acid esters, LiRR′B(O-i-Pr)2. Treatment of these complexes with an equivalent of anhydrous hydrogen chloride in ethyl ether liberates the borinic esters, RR′BO-i-Pr, and isopropyl alcohol, usually readily separated by distillation. Alternatively, treatment of the complexes with 1 mol of an appropriate acid chloride liberates the borinic esters, RR′BO-i-Pr, and an isopropyl ester, RCO2-i-Pr. By careful selection of the acid chloride, these two products can be easily separated by distillation. A careful examination of the reaction of other boronic esters in this reaction revealed that the boronic esters of 1,3-propanediol forms the 1:1 complex cleanly on reaction with organolithium compounds at -78 °C. (Formula Presented) Treatment of these ate complexes either with hydrogen chloride in ether or with an appropriate acid chloride provides the pure borinic ester. Consequently, simple rational procedures are now available for the synthesis in high purities and yields of either boronic or borinic acids and esters, either through hydroboration or through the use of organolithium compounds.
Organoboranes. 31. A simple preparation of boronic esters from organolithium reagents and selected trialkoxyboranes
Brown, Herbert C.,Cole, Thomas E.
, p. 1316 - 1319 (2008/10/08)
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. Protonation of this complex with anhydrous hydrogen 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.
