2001 cycloaddition reactions

cycloaddition reactionsO 0070

41 - 045Synthesis and Reactivity of Hexahydropyrroloquinolines. — Imines(I) derived from aromatic amines and either benzaldehydes or methylglyoxalateor 3-cyanoacrolein undergo formal [4+2] cycloaddition reaction with cyclicenamides (II) to give the title compounds as mixtures of diastereomers (III)and (IV). The cycloadducts derived from imine (If) are found to be veryunstable and give products (V) and (VI) under neutral or basic conditions.The cycloaddition fails for imine (Ie) bearing a strong electron-donatingsubstituent at the aldehyde component. From the reaction of enamide (IIa)and amine (VII), a known precursor of the corresponding imine derived fromformaldehyde, pyrroloquinoline (VIII) is obtained. — (HADDEN, MARK;NIEUWENHUYZEN, MARK; POTTS, DEIRDRE; STEVENSON, PAUL J.;THOMPSON, NORRIS; Tetrahedron 57 (2001) 26, 5615-5624; Sch. Chem.,Queen’s Univ., Belfast BT9 5AG, UK; EN)

1