New Wittig reagents, furanmethylids b-e were successfully developed. Their preparation, reactivity, and application toward the natural products synthesis are described in detail. (C) 2003 Elsevier Science Ltd. All rights reserved.
Synthesis and Photochemistry of Styryl Substituted Annelated Furan Derivatives
New beta-substituted benzo- and naphthofuryl derivatives (5, 6 and 7) of o-divinylbenzene, were synthesized and irradiated in order to form annelated bicyclo[3.2.1]octadienes. While 2-[2-(2-vinylphenyl)ethenyl]benzo[b]furan (5) upon irradiation gives the bicyclo[3.2.1]octadiene derivative (12) in 65% yield, 2-[2-(2-vinylphenyl) ethenyl]naphtho[2,1-b]furan (6) and 2-[2-(2-vinylphenyl)ethenyl]naphtho[1,2-b]furan (7), undergo cis-trans-isomerization but not form intramolecular photocycloaddition products. The mechanism of the intramolecular [2+2] photocycloaddition is explained via intermediate (17) which was proved by the formation of products (18) and (19), by irradiation in methanol and deuteromethanol.