1,3-Dipolar-cycloaddition of benzylazide to (+)-limonene: A protection cycle for the 8,9-double bond

A method for protecting the 8,9-double bond of (+)-limonene ( 1 ) is described. The key step is the 1,3-dipolar-cycloaddition of benzylazide to 1 , which affords N-benzyl-N-[9-(1-p-menthenylidene)]-amine ( 2 ) and N-benzyl-N-[8,9-(1-p-menthenylidene)]-amine ( 3 ).