Vinylogous Baylis-Hillman cyclization

The key tricyclic intermediate toward the total synthesis of spinosyn A was assembled by W.R. Roush et al. featuring a one-pot tandem intramolecular Diels-Alder reaction and an intramolecular vinylogous Baylis-Hillman cyclization. The cyclization precursor was prepared via the S-G modified HWE reaction. 

Roush and coworkers developed a new one-pot sequence consisting of an intramolecular Diels-Alder- and an intramolecular vinylogous Morita-Baylis-Hillman-cyclization for the synthesis of spinosyns [31]. These compounds are poly-ketide natural products possessing extraordinary insecticidal activity. 

Methot, J. L., Roush, W. R. Synthetic Studies toward FR182877. Remarkable Solvent Effect in the Vinylogous Morita-Baylis-Hillman Cyclization. Org. Lett. 2003, 5,4223-4226. 

An intramolecular vinylogous Morita-Baylis-Hillman reaction, followed by intramolecular aldol cyclization,129 is described under Intramolecular Aldols above. 

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