Reaction of 2-Butenoic Acid Dianion and Its N-(4-Methoxyphenyl)amide with Methoxy-Substituted Arynes

Article abstract of DOI:10.1021/jo00028a049

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) (85-90percent) and a N-(4-methoxyphenyl)-(E)-4-aryl-2-butenamide 9' (10-15percent).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 amountsof 4-aryl-2-butenoic acids 15'.The exclusive low temperature (-30 to -40 deg 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.