The reaction of atomic carbon and some of its daughter carbenes

The reaction of atomic carbon with styrene proceeds by addition to the vinyl double bond and insertion into a vinyl C-H bond. Double bond addition leads to the formation of phenylallene. The vinyl C-H insertion generates trans-1-phenylpropene-3-ylide, 31, and cis-1-phenylpropene-3-ylide, 32, as major products. Trans carbene, 31, gives phenylallene by hydrogen migration and trans-1-phenylpropene by abstraction of hydrogen. The cis carbene, 32, undergoes electrocyclic ring closure to indene. Examination of deuterium isotope effects in the reaction of atomic carbon with deuterated styrenes confirms these mechanisms. The reaction of 13C enriched carbon vapor with styrene demonstrates that phenylallene results from both double bond addition and vinyl C-H insertion. Carbenes 31 and 32 were also generated by the carbon atom deoxygenation of trans and cis 3-phenylpropenal and observed to undergo reactions consistent with the above mechanisms.;Benzocyclobutene reacts with atomic carbon to give indene and methylenebenzocyclobutene in a 11.6:1 ratio. The predominant indene production results from the interaction of the aryl pi-system and the empty p orbital of the carbene which brings about an intramolecular C-C insertion by the carbene. Reaction of cyclobutane with atomic carbon gives methylenecyclobutane, cyclopentene and bicyclo[2.1.0]pentane. The same products are formed in the deoxygenation of cyclobutane carboxyaldehyde by atomic carbon. Both reactions are postulated to proceed via cyclobutylcarbene.;The reaction of phenylcarbene with allyl ether gives allyl cyclopropylmethylether, 90, as major product of singlet carbene reaction. Lowering the temperature and adding triplet sensitizer increases the yield of triplet phenylcarbene which gives 7-phenyl-3-oxabicyclo[3.3.0]octane 91 by an initial addition to form a biradical followed by a radical cyclization. The total synthesis of the three diastereomers of new compound 91 was carried out.