Functionalized Cyclobutenes via Multicomponent Thermal [2 + 2] Cycloaddition Reactions.

Abstract

Cyclobutane derivatives Q 0022Functionalized Cyclobutenes via Multicomponent Thermal [2 + 2] Cycloaddition Reactions. -The reaction of an aldehyde, a secondary amine and a fumarate (or maleate) affords 3-aminocyclobutane-1,2-dicarboxylates as single isomers or diastereomeric mixtures. The conversion into the desired cyclobutenes is performed via methylation and elimination reactions. Products (VIII) derived from (IV) undergo ring opening at elevated temperature to give (Z,E)-dienes (IX). In contrast, cyclobutenes derived from isomers (V) react spontaneously to afford (E,E)-dienes (XI). -(SHELDRAKE, H. M.; WALLACE*, T. W.; WILSON, C. P.; Org. Lett. 7 (2005) 19, 4233-4236; Sch. Chem., Univ. Manchester, Manchester M13 9PL, UK; Eng.) -Klein 02-066