SYNTHESIS OF PENTACYCLO[4.3.0.02,5.03,8.04,7]NONANE (HOMOCUBANE) AND SOME OF ITS DERIVATIVES

Homocubane-4-carboxylic acid (6) has been prepared by two routes both of which utilize a Favorskii-type ring contraction of an α-halo ketone to generate the homocubane skeleton. In the preferred route, ketone 5, formed by photochemical ring closure of the Diels-Alder adduct, 4, of cyclopentadiene and α-bromocyelopentadienone, gave acid 6 (in nearly quantitative yield) when heated with aqueous alkali. In the alternate route, ketone 7, when heated with solid sodium hydroxide in benzene, gave a mixture of ring cleaved acid 8a and the desired Favorskii product 9a which was dehalogenated with lithium t-butyl alcohol to give acid 6. The latter was converted into the aminomethyl derivative 13, into the amine 14, and into the parent hydrocarbon, homocubane (17). When ketone 7 was heated either with an aqueous solution of potassium hydroxide or with solid potassium hydroxide in benzene, acid 8a was essentially the sole product. Nmr double resonance studies were carried out on ester 8b. © 1968, American Chemical Society. All rights reserved.