Diels-Alder reactions of heterocyclic aza dienes. Scope and applications

Reactions of unactivated olefins with Vilsmeier reagents

“…The X-ray structure determination demonstrates that the DielsAlder reaction occurs in a diastereofacially selective manner on the exo face of both diene and dienophile. Diels-Alder reactions with inverse electron demand involving a 2-azoniobutadiene unit as part of a quaternary heteroaromatic ring (30,31) or of N-arylimmonium ions (32) are well recognized, but we have not found any previous example in which the azoniobutadiene unit is acyclic. The interaction of perchlorate 11 with aqueous alkali solution yields the hydroxide adduct 12 (Scheme 2) which is easily reconverted into 11 by treatment with 70% perchloric acid in ethanol solution.…”

Regioselective inverse Diels-Alder reaction of unsymmetrical tetrazines with aldehydes and ketones

“…[1][2][3][4] The reaction goes through two steps: an inverse-electron-demand Diels-Alder reaction (iDA) and a retro Diels-Alder (rDA) reaction, which results in the loss of a nitrogen molecule to produce pyridazine as the final product. 5 Due to the high efficiency of this reaction under mild conditions, it can be considered as a type of "Click Chemistry", [6][7][8][9] and recently has been widely used in the synthesis of heterocyclic compounds, 10 in bioconjugation applications, [11][12] as well as in the modulation of fluorescence of dyes for bioimaging applications.…”

Microwave assisted efficient one-pot synthesis of 3,5,6-trisubstituted-1,2,4-triazines from fatty acid hydrazides under solvent-free conditions and their antimicrobial activity

“…1,2,4-Triazines are a representative class of heterocyclic compounds with a wide variety of interesting properties which are used in medicine and agriculture. [9][10][11][12] It has been associated with diverse pharmacological activities such as hypertension and inhibition of platelets, 13 antileukemic, 14 antiinflammatory 15 and potent neuroprotective agents. 16 The 1,2,4-triazine moiety is a structural element in antimalarial, 17 anticancer, 18 antifungal, 19 anticonvulsant, 20 antibacterial, 21 In view of above mentioned pharmacological importance of heterocycles and our ongoing efforts to synthesize heterocycles from fatty acids [36][37][38][39] we now describe an expeditious ecofriendly solvent-free microwave accelerated solid state approach for the rapid synthesis of 3,5,6-trisubstituted-1,2,4-triazines from saturated and olefinic fatty acid hydrazides wherein several disadvantages such as long reaction time and tedious work-up are avoided.…”