Sporidesmins. XIX. The diazotization and coupling in acid of p-Nitro- and 2,4-Dinitro-aniline to veratrole or guaiacol: ¹H N.M.R. of the products in deuterochloroform and deuteroacetone

Abstract

p-Nitrobenzenediazonium chloride in conc. HCl coupled to guaiacol (2-methoxyphenol) to give 4-hydroxy-3-methoxy-4'-nitroazobenzene, but did not couple to veratrole (1,2-dimethoxybenzene). 2,4-Dinitroaniline, diazotized in conc. HCl with no urea added, yielded 2-chloro-4,5-dimethoxy- 2',4'-dinitroazobenzene with neat veratrole. However, 2,4-dinitroaniline, diazotized in conc. HCl and then treated with urea, yielded 2-chloro-4-nitrobenzenediazonium chloride which again coupled in acid with guaiacol to give 2-chloro-4'-hydroxy-3'-methoxy-4-nitroazobenzene but not with veratrole in acetic acid. Veratrole added to 2,4-dinitrobenzenediazonium phosphate or trichloroacetate in acid media yielded 3',4'-dimethoxy-2,4-dinitroazobenzene. These 2,4-dinitrobenzenediazonium salts coupled to guaiacol giving 4'-hydroxy-3'-methoxy-2,4-dinitroazobenzene. p-Nitrobenzenediazonium and 2-chloro-4-nitrobenzenediazonium salts in acid gave the Gomberg reaction with veratrole forming the corresponding biphenyls. The ¹H n.m.r. spectra of all the products obtained in this investigation and the deshielding effect of deuteroacetone on four of the compounds are discussed. The deuterochloroform spectrum of 4'-hydroxy-3'-methoxy-2,4-dinitroazobenzene at 60 MHz shows an anomalous set of 26 or more lines that are not attributable to a quinone hydrazone structure.