1. Homologation Strategy for the Generation of 1-Chloroalkyl Radicals from Organoboranes
- Author
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Gong Xu, Jacqueline Habegger, Monique Lüthy, and Philippe Renaud
- Subjects
010405 organic chemistry ,Chemistry ,Radical ,Organic Chemistry ,Enantioselective synthesis ,Halogenation ,Optically active ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Styrene ,chemistry.chemical_compound ,Hydroboration ,Reaction sequence ,540 Chemistry ,570 Life sciences ,biology ,Organic chemistry ,Catecholborane - Abstract
The generation of 1-bromo and 1-chloroalkyl radicals from organoboranes has been investigated. The direct approach involving the hydroboration of halogenated alkenes is impeded by partial dehalogenation taking place during the hydroboration process. An indirect method involving the generation of B-(1-chloroalkyl)catecholborane by homologation of B-alkylcatecholborane with dichloromethyllithium was developed. A reaction sequence involving a hydroboration reaction, a Matteson homologation, and a radical allylation process has been performed as a one-pot process that takes advantage of three different reactivities of organoboron species. Starting from styrene derivatives, it was possible to prepare B-(1-chloro-2-arylpropyl)catecholboranes that are excellent precursors to 1-chloro-2-arylpropyl radicals. A concise approach for the synthesis of an optically active α-methylene-γ-lactone from p-chlorostyrene has been developed on the basis of a two-step sequence involving an enantioselective hydroboration-homologation-cyclization reaction followed by a hydrolysis-lactonization process.
- Published
- 2016