PENTACYCLODECANE CHEMISTRY .V. SYNTHESIS AND ACETOLYSIS OF SYN-AND ANTI-PENTACYCLO[5.3.0.0.2,5.03,9.04,8]DEC-6-YL P-TOLUENESULFONATE . EVIDENCE CONCERNING INTERMEDIACY OF BRIDGED CARBONIUM IONS

The syn and anti isomers of pentacyclo[5.3.0.02,5• 03,9•04,8]decan-6-ol were synthesized by irradiation of syn-and anti,endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-ol, respectively, in acetone solution. Solvolysis of the syn pentacyclodecyl tosylate in unbuffered acetic acid gave almost exclusively the unrearranged syn acetate. Acetolysis of the anti tosylate gave mainly the rearranged pentacyclo[5.3.0.02,6•03,9•04,8]dec-6-yl acetate accompanied by 15% of unrearranged anti acetate. Internal return with rearrangement occurred with the anti tosylate. The rates of acetolysis of the syn and anti tosylates were measured; rate accelerations of 1.3 × 104 and 5 × 103, respectively, over those predicted for unassisted solvolysis were calculated from Schleyer's equation. Reduction of pentacyclo[5.3.0.02,5.03,9.04,8]decan-6-one with sodium borohydride, lithium aluminum hydride, and lithium tri-t-butoxy aluminum hydride gave 76-80:24-20 ratios of syn and anti alcohols, respectively. The rate of borohydride reduction was determined, and an attempted correlation with the solvolysis rates was made. Equilibration of the syn and anti alcohols with aluminum isopropoxide-acetone gave a 50:50 mixture. The solvolysis reactions are best interpreted in terms of bridged carbonium ion intermediates, although other explanations cannot be ruled out entirely. © 1969, American Chemical Society. All rights reserved.