REACTION OF 2-BUTENOIC ACID DIANION AND ITS N-(4-METHOXYPHENYL)AMIDE WITH METHOXY-SUBSTITUTED ARYNES

N-(4-Methoxyphenyl)-1-butenamide dianion (6), generated by the reaction of N-(4-methoxyphenyl)-2-butenamide (3) with LDA or LTMP, undergoes exclusive 4-arylation with various methoxy-substituted arynes 2a-e yielding mixtures consisting of a N-(4-methoxyphenyl)-(E)-4-aryl-3-butenamide 9 (85-90%) and a N-(4-methoxyphenyl)-(E)-4-aryl-2-butenamide 9' (10-15%). Under certain conditions, 4,4-diarylated products 12 are also obtained. 2-Butenoic acid dianion (14) also reacts with methoxy-substituted arynes affording predominantly 4-aryl-3-butenoic acids 15 and minor amounts of 4-aryl-2-butenoic acids 15'. The exclusive low temperature (-30 to -40-degrees-C) 4-addition of arynes to dianion 14 is in contrast to the predominant 2-addition that 14 undergoes with certain aldehydes and ketones at comparable temperatures. The mixtures of 4-arylbutenoic acids 15 and 15' and 4-arylbutenamides 9 and 9' were readily hydrogenated (Pd/C) and esterified (MeOH/H2SO4) to synthetically valuable methyl 4-arylbutanoates 17.