Diazonium salts Diels-Alder reactions

The cycloaddition between furan and maleic anhydride was the first uncatalyzed aqueous Diels-Alder reaction reported in the literature and was studied by Diels and Alder themselves [11]. This cycloaddition was successfully revised by Woodward and Baer [12] and some years later by De Koning and coworkers [13]. The aqueous medium was also used in the cycloaddition of aromatic diazonium salts with methylsubstituted 1,3-butadienes [14]. 

A pyridazine ring can be formed in a cycloaddition reaction of diazo compounds or diazonium salts, with alipahtic or cyclic azo compounds. It can also be formed by cycloaddition of various 1,2,4,5-tetrazines and dienophiles in inverse electron demand Diels-Alder reactions. As shown later, this synthetic approach has been used extensively and with success in the 1980s. 

Deuteration of arenes, 206 Deuterium, role in nmr, 243 Dextrorotatory, 70 Diastereomers, 69 conformational, 80 Diastereoselective reactions, 91 Diazine, 458, 460 Diazomethane, 67, 353 Diazonium ions, 409 Diazonium salts, 416 Dicarboxylic acids, 342 Diels-Alder reaction, 154 Dienes, polymerization, 153j summary of chemistry, 154 Dienophile, 154 Dihalides, dehalogenation, 91 Dimethyl sulfoxide (DMSO), 305 Dioxane, 285 Dioxin, 447... 

The research team of J.E. Baldwin developed the first synthetic sequence for the preparation of N(5)-ergolines. The key step was a hetero-Diels-Alder reaction of a substituted phenyl butadiene to form the piperidine ring. The phenyl butadiene substrate was prepared via the Meerwein aryiation of 1,4-butadiene and a diazonium salt derived from 2,6-dinitrotoluene. The initially formed chlorinated product was subjected to dehydrochlorination using DBU as the base. 

Sol 7. (d) Diazotization of anthranilic acid gives a diazonium salt, which on treatment with a mild base undergoes elimination of CO2 and N2 to give benzyne intermediate (I). It immediately undergoes Diels—Alder reaction to... 

X = S) reacts with diazonium salts to form 5-arylhydrazones, and is 5-aminomethylated under Mannich conditions. The dioxo analogue, however, does not take part in the second two reactions <87MI 302-01) (Scheme 71). 2-Alkylideneimidazolidines take part in inverse Diels-Alder synthesis <87TL2681, 87TL6027>, and they are C-alkylated by alkyl halides in neutral media <94H(37)1233>. 

---