2002 cycloaddition reactions

cycloaddition reactionsO 0070

39 - 041Intramolecular Diels–Alder Reactions Using α-Methylene Lactonesas Dienophile. — Zn-mediated coupling of the dienals (I), (V), and(VIII) with the acrylate (II) leads to hydroxy esters of type (IX) which easilyundergo lactonization giving α-methylene lactones having a dienyl side chain.Intramolecular Diels–Alder reaction of the latter offers an efficient approachto tricyclic compounds such as (IV), (VII), and (XI). In most cases, thisreaction proceeds with high diastereoselectivity. However, starting from eductsbearing a furan side chain and a densely functionalized tether connecting theα-methylene lactone and diene no intramolecular Diels–Alder reaction is ob-served. — (RICHTER, FRANK; BAUER, MATTHIAS; PEREZ, CAROLINE;MAICHLE-MOESSMER, CAECILIA; MAIER, MARTIN E.; J. Org. Chem.67 (2002) 8, 2474-2480; Inst. Org. Chem., Eberhard-Karls-Univ., D-72076Tuebingen, Germany; EN)

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