Pd-catalyzed reactions of donor-acceptor-substituted cyclopropanes and their ring-opened derivatives: Attempted Heck cyclization and novel one-pot enolate arylations

Donor-acceptor substituted cyclopropane derivatives 4a-g were synthesized i n good yields from ketones, via the corresponding silyl enol ethers 2a-g, b y cyclopropanation with methyl diazoacetate followed by alkylation using o- iodobenzyl iodide. The gamma -oxo esters 5a-g were prepared in high yield, employing NEt3.3HF. A novel Pd-catalyzed one-pot transformation of 4a-f int o 1,2-disubstituted indanes 6a-f was accomplished using either CsF (Method A or B) or Bu4NF (Method C) as the fluoride source to achieve the in situ r ing-opening of 4a-f. The two reagents CsF and Bu4NF function in a complemen tary manner. For example, CsF works better with enones 4b and 4c, while Bu4 NF functions well with aryl/alkyl ketones 4d-f. Pd-catalyzed Heck cyclizati on of vinyl ketone 5a furnished mainly the 7-exo-trigcyclization product 7 but isopropenyl ketone 5b gave a moderate yield of indane derivative 6b, ar ising from enolate arylation. When the carbonyl group in 5b was protected, a novel tricyclic compound 13 was obtained in low yield.