ChemInform Abstract: Organocatalyzed Formal [4 + 2] Cycloaddition of in situ Generated Azoalkenes with Arylacetic Acids: An Efficient Approach to the Synthesis of 4,5‐Dihydropyridazin‐3(2H)‐ones.

Abstract

Organocatalyzed Formal [4 + 2] Cycloaddition of in situ Generated Azoalkenes with Arylacetic Acids: An Efficient Approach to the Synthesis of 4,5-Dihydropyridazin-3(2H)-ones. -The reaction is suitable for the preparation of various target compounds, inter alia scaffolds of a broad spectrum of pharmaceutical agents. Preliminary studies reveal the possibility of a successful asymmetric version [cf. (IIIa)]. Some derivatizations of racemic derivative (IIIa) are also presented. -(LI, X.; GAI, K.; YUAN, Z.; WU, J.; LIN*, A.; YAO, H.; Adv. Synth. Catal. 357 (2015) 16-17, 3479-3484, http://dx.

Recent Advances in the Chemistry of Conjugated Nitrosoalkenes and Azoalkenes

“…There are a few examples of formal [4 + 2] cycloaddition reactions to obtain highly substituted tetrahydropyridazines that otherwise would not be possible. Thus, reactions of azoalkenes toward dehydroalanine esters, 87 arylacetic acids, 88 and maleimides 89 have been described.…”

[4 + 2] Annulation Reaction of In Situ Generated Azoalkenes with Azlactones: Access to 4,5-Dihydropyridazin-3(2H)-Ones

“…7 Surprisingly, there exists only one report by Yao and co-workers, who realized the formal [4 + 2] cycloaddition of azoalkenes with arylacetic acids under the catalysis of isothiourea to access 4,5-dihydropyridazin-3(2H)ones (Scheme 1b). 9 On the other hand, azlactones have been proved to be a robust and versatile two-carbon synthetic building block and have found wide application in the construction of lactam compounds. 10,11 By this token, azlactone serving as a two-carbon synthon can first react with a wide variety of electrophiles from its α-position.…”