Oxidation of azines with lead tetraacetate

Contributions to the chemistry of 3‐cyanoacetylhydrazono‐2‐indolinones and X‐ray structure of Z‐3‐cyanoacetylhydrazono‐2‐indolinone monohydrate

“…The cold residue was triturated with water (∼50 mL), and the undissolved was filtered off, washed with water and hexane and dried in a vacuum desiccator to give crude Na-salt of 4b (0.528 g; 79%), mp >360 • C. Anal. Calcd for C 15…”

“…They can be prepared by cycloaddition of 3,3-disubstituted diazirenes to diacyldiazenes [1][2][3][4][5][6][7][8][9][10][11][12], that of aldehydes to nitrilimines [13], or a ketene to a ketone acylhydrazone [14]. Other methods to prepare such compounds include Pb(OAc) 4 oxidation of aldazines [15], treating silver salt of acylhydrazones with acid chloride [16]. More conveniently, a reaction of (acyl)hydrazones with acid chlorides [10,11], as well as with acid anhydrides-either by itself or in the presence of a base and Lewis or protic acid, respectively [17][18][19][20]-also gives 3-acyl-1,3,4-oxadiazoline derivatives.…”

Type 2 Intramolecular N-Acylazo Diels−Alder Reaction: Regio- and Stereoselective Synthesis of Bridgehead Bicyclic 1,2-Diazines

“…The reactivity of the N-acylazo functional group towards thermal decomposition and cycloaddition was not known; therefore a search for mild reaction conditions was undertaken. Typically, N-acylazo dienophiles are generated by oxidation of N-acylhydrazides with tert-butylhypochlorite 11 , lead tetraacetate 12 , or potassium ferricyanide 13 . Oxidation of hydrazide 8 with Pb(OAc) 4 resulted in a complex mixture of products.…”

Studies on the Synthesis of 2-Alkyl-5-aryl-1,3,4-oxadiazolines from N-Acylhydrazones

“…7 Other methods include oxidative cyclization of aldazines using Pb(OAc) 4 . 8 On the other hand, the formation of similar structures is described for reactions involving ketenes (generated in situ) and N-acylhydrazones or 2,3-diaza-1,3-dienes (azines) either with moderate to good yields or as by-products. 9 The absence of reports for the synthesis of simple 2-alkyl-5-arylderivatives is noteworthy.…”