AN IMPROVED SYNTHESIS, MOLECULAR-STRUCTURE, AND PROPERTIES OF 1,4-DIHYDRO-DICYCLOPROPA[B,G]NAPHTHALENE

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 C2h symmetry in the crystal lattice with the space group P2(1)/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.