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Categories: C-C Bond Formation > Cyclic compounds > Cycloalkenes

Synthesis of cycloheptenes and higher homologues

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The reaction of organocerium reagents, generated in situ from aryl and heteroaryl lithium compounds, with cycloalkanones proceeds cleanly to provide alkoxides. Addition of MsCl or SOCl2 with DBU gave aryl-substituted cycloalkenes in good yields. A short total synthesis of (±)-laurokamurene B is described.
J. Tallineau, G. Bashiardes, J.-M. Coustard, F. Lecornué, Synlett, 2009, 2761-2764.


In situ generation of allylic boronates by iridium-catalyzed borylation of cyclic alkenes in the presence of additives, such as methylimidazole and DBU, followed a reaction with aldehydes allows the synthesis of stereodefined homoallylic alcohols. Cycloalkenes without additives as well as acyclic substrates gave vinylic boronates, which were coupled with organohalides in a Suzuki-Miyaura sequence.
V. J. Olsson, K. J. Szabó, J. Org. Chem., 2009, 74, 7715-7723.


TFA-promoted exo carbocyclizations of nonterminal alkynals gave good to excellent yields of exo cycloalkenones. On the other hand, terminal 5-alkynals gave endo carbocyclizations to cyclohexenones. These carbocyclizations can be considered as tandem alkyne hydration/aldol condensation processes.
C. González-Rodríguez, L. Escalante, J. A. Varela, L. Castedo, C. Sáa, Org. Lett., 2009, 11, 1531-1533.


[ReBr(CO)3(thf)]2 catalyzes the reaction of a 1,3-dicarbonyl cyclic compound with an acetylene to give a medium-sized cyclic compound in excellent yield. By using isocyanide as an additive, the insertion of acetylenes into a carbon-carbon single bond occurs under mild conditions.
Y. Kuninobu, A. Kawata, K. Takai, J. Am. Chem. Soc., 2006, 128, 11368-11369.