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,

The application of the intramolecular [4 + 2] cycloaddition of the enamido diene 6 to the construction of the unsaturated oxolycorane 2 is described, thereby completing a novel, formal synthesis of the Amaryllidaceae alkaloid lycorine (1).Sir: The assemblage of functionalized hydroquinolines and hydroindoles, which are structural elemento common to many alkaloid natural products, via the intramolecular [4 + 2] cycloadditions2 of dienamides is firmly established,3 but the feasibility of employing enamides as dienophiles in [4 + 2] cycloadditions for the construction of these heterocyclic synthons has only been recently recognized.4,5 Consequently, wé now report a novel synthesis of the unsaturated lactam 2 by a route which features the intramolecular cycloaddition of an enamide with an unactivated diene as the key step. Since 2 has been previously con-verted6 7*® to lycorine (l),6,7 an alkaloid of the Amaryllidaceae(1) Portions of this work were previously presented at the Second Chemical Congress of the North American Continent, Las Vegas, NV, August 1980, ORGN 155.(2) For reviews of intramolecular Diels-Alder reactions, see (a) Oppolzer, W.

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Aus den Dienen (I) erhält man mit Schwefeldioxid die Dihydro‐thiophene (II), die mit dem 1‐Methyl‐3,4‐dihydro‐isochjnolin (III) zu Addukten (IV) reagieren.

Der Versuch, die Diene (I) mit dem Methyldihydroisochinolin (II) zu den Derivaten (III) zu kondensieren, die dann unter intramolekularer [4 + 2]‐Cycloaddition die mit Erythrina‐Alkaloiden strukturell verwandten tetracyclischen Spirane (IV) geben könnten, gelingt nicht.