Highly Enantioselective [4 + 2] Cycloaddition Reactions Catalyzed by a Chiral N-Methyl-oxazaborolidinium Cation
Organic Letters2008Vol. 10(15), pp. 3271–3273
Citations Over TimeTop 10% of 2008 papers
Abstract
The reaction of lithium aryl borohydrides with salts of beta-amino alcohols provides a new route for the synthesis of oxazaborolidines. This method also leads to the first synthesis of hitherto elusive N-methyl oxazaborolidine cations, specifically the cationic proline derivative 3. Compound 3 is a strong chiral Lewis acid which is very effective for catalysis of [4 + 2]-cycloaddition reactions in good yield and with high enantioselectivity. Several diverse examples illustrate the scope of these catalytic reactions.
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