During the course of a broad investigation of the intramolecular [4 + 2] cycloaddition reactions of enamines and enamides with unactivated butadienes, efforts were directed toward the construction of the spirocycles 10a and 10b which possess the molecular framework characteristic of the Erythrina alkaloids. Whereas it was not possible to prepare the requisite enamino diene 9a or the enamido diene 9b by the reaction of 1 -methyl-3,4-dihydroisoquinoline (8) with 3,5-hexadienyl triflate (6) or 3,5-hexadienoyl chloride (7), the enamine 16a and the enamide 16b, in which the dienoic moiety is expeditiously masked as a sulfolene derivative, were readily produced upon coupling 8 with the triflate 14b or the acid chloride 15b. Interestingly,

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Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for the support of this research.(11) Thus far, efforts to detect a stabilized ylide intermediate have not been successful; this suggests that ring opening may be the rate limiting step in these reactions.(12) Carboethoxycyclobutyltriphenylphosphonium fluoroborate ( 17) may be prepared from cyclobutyltriphenylphosphonium bromide13 by a procedure analogous to the one used for the synthesis of 2 (17: 63 % yield (mp 162-163°)).

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