An Improved Synthesis, Molecular-Structure, and Properties of 1,4-Dihydro-Dicyclopropa[b,g]naphthalene

Abstract

A marked improvement in the preparation of 1,4-dihydrodicyclopropa[ b,g ]naphthalene (4) from isotetralin (7) has been achieved by selecting conditions which avoid the unwanted olefin (12). The easily available dicycloproparene (4) has C_2h symmetry in the crystal lattice with the space group P2₁/n. The geometry is readily rationalized by the concept of 'bent bonds' that are also suggested by X-X difference electron density maps. Cheletropic biaddition of dichlorocarbene to (4) provides the dicyclobutanaphthalenes (15) and (16). Attempted Petersen olefination to mono- and di-alkylidene derivatives, e.g. (21) and (22), is foiled by a reluctance of (4) to provide an easily interceptible anion.