CAGE ENLARGEMENT OF (HYDROXYMETHYL)PENTACYCLO[4.2.0.0.2,5.0.3,8.0.4,7] OCTANE TO A TETRACYCLO[4.3.0.0.3,9.0.4,7] NONANE SYSTEM IN FORMIC-ACID

Cationic rearrangement of thyl)pentacyclo[4.2.0.0(2,5).0(3,8).0(4,7)]o ctanes (1) in formic acid gave new cage compounds, rmyloxy)tetracyclo[ 4.3.0.0(3,9).0(4,7)]nonan-7-ols (3) and new cage-degradation products, rylmethylene)-2-cyclobutenyl]-2-cyclopenten-1-ones (4) along with Wag ner-Meerwein rearrangement products, pentacyclo[5.3.0.0(2,5).0(3,9).0( 4,8)]decanes (5; C2-bishomocubanes) and pentacyclo[5.3.0.0(2,6)0(3,9)0 (4.8)]decanes (6; D2h-bishomocubanes). )pentacyclo[4.3.0.0(2,5).0(3,8) .0(4,7)]nonan-1-ols (2) gave 4, 5, and 6 without the formation of 3. A Wagner-Meerwein 1,2-bond shift of 1 gave key intermediates 2 which we re converted into 3 via homoallylic rearrangement, into 4 via pinacol- pinacolone-like rearrangement, or into 5 and 6 via Wagner-Meerwein rea rrangement.