Conjugated azoalkenes. Part II. Synthesis of some heterocyclic azoalkenes

Abstract

The synthesis of a new class of unknown heterocyclic conjugated azoalkene derivatives is reported.

One‐Pot Synthesis of Imidazole‐4‐Carboxylates by Microwave‐Assisted 1,5‐Electrocyclization of Azavinyl Azomethine Ylides

“…1,2‐Diaza‐1,3‐dienes (DDs) 1a , b were synthesized as already described and occur both as a mixture of E / Z isomers 12. Whereas DD 1b is a shelf‐stable red crystalline compound,12b DD 1a 12a is a somewhat unstable red liquid that tends to decompose upon prolonged storage. Therefore, 1a was always generated in situ by treatment of the parent chlorohydrazone with triethylamine in acetonitrile at room temperature, and the resulting red solution was used as such for the subsequent chemistry without further purification.…”

1,2-Diaza-1,3-butadienes: just a nice class of compounds, or powerful tools in organic chemistry? Reviewing an experience

“…69 The mono-1,4-adducts, 3, still having an active hydrogen (R 6 =H), can provide the bis-1, 4-adducts, 4, by further 1,4-addition of the same or different DBD molecule (R 1' , R 2' , R 3' = or ≠ R 1 , R 2 , R 3 ). 27,56,58,62 In the case of triphenylphosphine, [53][54][55] nitro-, 61,67 phenylsulfonyl-, p-chlorophenylsulfonyl-, p-toluenesulfonyl-, phenylsulphinyl-, 67 and halogen-68 derivatives in which R 4 is a leaving group, α,β-unsaturated hydrazones, 5, were obtained (Scheme 3). …”

“…2-Hydroxy-1-aminopyrrolines, 14, and 1-aminopyrroles, 15, were synthesized by reaction of DBD, 1, with β-diketones, β-keto esters, 15,17,18,22,[29][30][31][32][33][34][35][36][37][38][39]42,43,67,90 β-keto amides, [8][9][10]18,22,28,38,[46][47][48][49]67 β-keto lactones, 37 β-keto phosphoranes, 55 β-nitro ketones, 61,67 β-keto sulfones, [50][51][52]67 β-cyano ketones, 58,59,67 remotely activated ketones, 60 β-keto phosphonates, 62 α,α-dichloroacetophenone, 13, 68 …”

FeCl3‐Catalyzed Formal [3+2] Cyclodimerization of 4‐Carbonyl‐1,2‐diaza‐1,3‐dienes

“…Over the years, the 1,2‐diaza‐1,3‐butadienes [22] (DDs), also called azoalkenes, have proven to be versatile and multifaceted starting materials for the construction of several heterocyclic frameworks by reactions with nucleophilic agents [23] . In particular, DDs are excellent precursors of pyrroles, and several synthetic pathways with different partners such as enamines, [24] β‐dicarbonyl compounds, [25] β‐ketosulphones, [26] α‐oxophosphoranes, [27] activated nitriles, [28] aldehydes, [29] silyl enol ethers, [30] Danishefsky's dienes, [31] or 1,3‐bis(silyloxy)‐1,3‐butadienes [32] have been developed. DDs can also react with themselves providing tetrahydropyridazines, as reported in two quite recently published papers.…”