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Title: Reaction of hindered organoboranes
Author: Zhao, J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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Organoboron chemistry, including the synthesis and some applications of organoboron compounds, especially hindered arylboranes, which relate to the background of this research work, is briefly reviewed in the first two chapters. Chapter 3 introduces successful methods for the preparation of two new hindered monoarylboranes, ArBH2, tripylborane and mesitylborane. It includes two approaches, one being the redistribution of Ar2BH and BH3-THF and the other via dimethoxyarylboranes. Mesitylborane, MesBH2, is the first monoorganoborane which exists in crystalline form. Chapter 4 introduces a stability study of ArBH2. By means of hydrolysis-gas titration and methanolysis-GC analysis, it was shown that TripBH2 and MesBH2 are far more stable than thexylborane. The hydroboration properties of TripBH2 and MesBH2 are described in Chapter 5. Tripylborane and mesitylborane hydroborate two equivalents of terminal alkenes or cyclohexene to give the corresponding ArBR2. Oxidation gives high yields of alcohols. Tripylborane and mesitylborane possess sequential hydroboration properties which allow the preparation of ArBR1R2 (R1,R2= primary alkyl or cyclohexyl). Chapter 6, describes the cyanoborate process on ArBR1R2, which allows the formation of ketones R1R2CO. No aryl group migration is found. Chapter 6 also introduces the hydroboration of dienes with mesitylborane and subsequent cyanoborate process. When (+)-limonene was used, low yields of ketones were obtained. When 4-vinylcyclohexene was used, bicyclo[3.2.2]nonan-2-one was produced in 48% yield. Novel methods of synthesis of mixed triorganoboranes from ArBH2 are introduced in Chapter 7. The methods involve the preparation of ArBR1R2, then aryl group replacement, for example by organolithium compounds, e.g. BunLi to form BunR1R2B. The aryl group in ArBR1R2 can also be replaced by bromination. Subsequent reaction with a Grignard reagent, R3MgBr, yields R1R2R3B. The preparation and some reactions of mesitylisopinocampheylborane, Ipc(Mes)BH, are described in Chapter 8.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available