Hydroxylation of 1-azabicyclo[4.1.0]hept-3-enes Formed by Diels-Alder reactions of benzyl 2H-azirine-3-carboxylate

Benzyl 2H-azirine-3-carboxylate 1b added as a dienophile to several cyclic and acyclic conjugated dienes at room temperature to give derivatives of the 1-azabicyclo[4.1.0]hept-3-ene ring system. The cycloaddition reactions gave exclusively the products of endo addition with respect to the three membered ring, as shown by crystal structures of two of the compounds, 4c and 4d. Methods for the cis-hydroxylation of the double bonds of some of these compounds were explored and four dihydroxy compounds were isolated from the adducts with cyclohexa-1,3-diene, 1-acetoxybutadiene, 1,4-diacetoxybutadiene and 1,4-bis(tertbutyldimethylsilyloxy) butadiene, in each case as single isomers. The structure of one of these, compound 6, was supported by an X-ray crystal structure determination. Methods for reduction of the benzyloxycarbonyl group to a hydroxymethyl group were also investigated with the aim of forming novel glycosidase inhibitors analogous to nojirimycin.