Aza-Morita−Baylis−Hillman Reactions and Cyclizations of Conjugated Dienes Activated by Sulfone, Ester, and Keto Groups

The aza-Morita−Baylis−Hillman reactions of aldimines 2 with several activated conjugated dienes were
found to proceed smoothly in DMF in the presence of 3-hydroxyquinuclidine (HQD). Imines 2 reacted
with 1-(p-toluenesulfonyl)-1,3-butadiene (3), methyl 2,4-pentadienoate (6), hexa-3,5-dien-2-one (7), and
1-phenylpenta-2,4-dien-1-one (8) to afford adducts 4, 13, 14, and 15, respectively. While products 4, 13,
and 15 were formed as E,Z mixtures, adducts 14 were obtained as essentially pure E-isomers. Cyclization
of the E-isomers of the products derived from the dienyl sulfone 3 and the dienoate ester 6 occurred via
intramolecular conjugate addition under base-catalyzed conditions to afford functionalized piperidines 5
and 16, respectively. The aza-Morita−Baylis−Hillman reaction and subsequent cyclization of the imine
2a with 3 were also carried out as a one-pot reaction, while the reaction mixture was simultaneously
irradiated at 300 nm to effect the photoisomerization of the unreactive Z-adduct of the corresponding 4
to the more reactive E-isomer.

醛亚胺2与多种活化共轭二烯烃的氮杂Morita-Baylis-Hillman反应（aza-Morita−Baylis−Hillman reaction），在3-羟基奎宁环（3-hydroxyquinuclidine, HQD）存在下，于N,N-二甲基甲酰胺（DMF, N,N-Dimethylformamide）中可顺利进行。亚胺2分别与1-(对甲苯磺酰基)-1,3-丁二烯（1-(p-toluenesulfonyl)-1,3-butadiene, 3）、2,4-戊二烯酸甲酯（methyl 2,4-pentadienoate, 6）、己-3,5-二烯-2-酮（hexa-3,5-dien-2-one, 7）以及1-苯基戊-2,4-二烯-1-酮（1-phenylpenta-2,4-dien-1-one, 8）反应，分别得到加合物4、13、14和15。尽管产物4、13和15以E,Z异构体混合物的形式生成，加合物14几乎仅得到纯的E型异构体。由烯基砜（dienyl sulfone）3与二烯酸酯（dienoate ester）6得到的产物的E型异构体，在碱催化条件（base-catalyzed conditions）下通过分子内共轭加成（intramolecular conjugate addition）发生环化，分别得到官能化哌啶（functionalized piperidines）5和16。亚胺2a与3的氮杂Morita-Baylis-Hillman反应及后续环化也可通过一锅法反应（one-pot reaction）完成，同时在300 nm波长下照射反应混合物，将对应的4中非反应性的Z型加合物光异构化（photoisomerization）为反应性更强的E型异构体。