Phosphoranes, hydrazones

Attempted cyclization of 233 with alkali afforded 234 in addition to 238, resulting from the elimination of one molecule of water from the hydrazone residue and the quinoxalinone ring and simultaneous hydrolysis of the ester group. This indicated the presence of two competitive reactions under conditions of cyclization. The structure of 234 was proved by its preparation by hydrolysis of 235. The latter was prepared by the reaction of aldehyde 237 with the phosphorane. The structures were confirmed by studying their H-NMR and mass spectra. 

Examples of substrates [23] with heteroatom double bonds (C = X) are presented in the rosette of Scheme 5. Here we feature the efficient denitrogenation of diazoalkanes, diazoquinones, the hydrazone of benzil, and benzophenone oxime into the respective carbonyl products [23]. On the other hand, the bis-oxime afforded furoxane, while the phosphorane led to methyl maleate on elimination of triphenylphosphine oxide [23], Thiones are oxidized to the corresponding S-oxides and the iodonium ylide yields the labile w c-trione [23],... 

When reviewed in CHEC-I some examples of cyclization y to the heteroatom had been described for the synthesis of pyridazines, but the method was of most importance in the synthesis of cinnolines. Examples of pyridazine syntheses included cyclization of ketazines with EDA, and intramolecular Wittig reactions of phosphoranes derived from phosphacumuleneneylides and the hydrazones produced from 1,3-dicarbonyl compounds and aryldiazonium salts. Synthetically useful approaches to cinnolines given include the intramolecular Friedel-Crafts acylation of the diacid chlorides derived from the condensation products of aryldiazonium salts and diethyl malonate to give 4(l//)-cinnolinones, and thermal cyclization of iminium hydrazones obtained from enamine esters and aryldiazonium salts. 

Phosphoranes, alkylidene-. See Phosphonium,... Phosphoranes, (alkylideneazino)-. See Ketones, (triphenylphosphoranylidene)hydrazones Phosphoric acid, 4-chlorophenyl esten nucleoside coupling with, 217-218 —, esters (See also Nucleotides) ... 

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