Rearrangement of N-Oxyenamines and Related Reactions

Abstract

CONTENTS 5458 5.1. Boekelheide Rearrangement 5458 5.2. Rearrangement of Nitrones and Related Compounds 5461 6. Miscellaneous Pericyclic Reactions of N-Oxyenamines 5466 7. Conclusions 5469 Author Information 5469 Corresponding Author 5469 Notes 5469 Biographies 5470 Acknowledgments 5470 Abbreviations 5470 References 5470

Synthesis and reactivity of heterocyclic hydroxylamine-O-sulfonates

“…As shown in Scheme 7, the reaction of D with CS 2 carried out in DMF in the presence of triethylamine gives 6,7-dihydro-5H-imidazo [2,1- nucleophilic addition-electrophilic amination reaction, which is mechanistically related to the formation of oxadiazoles 10-17 described above. By contrast, compound D in aqueous NaOH solution, which is more effective than DMF at solvating atoms with partial negative charges, undergoes a reaction with two molecules of carbon disulfide that, after desulfurization, gives 7,8-dihydroimidazo[1,2-c] [1,3,5]thiadiazine-2,4(6H)-dithione (19). The reaction of hydroxylamine-O-sulfonate D with aryl isothiocyanates is strongly dependent on stoichiometry of the reagents and temperature (Scheme 8).…”

“…The reaction of hydroxylamine-O-sulfonate D with aryl isothiocyanates is strongly dependent on stoichiometry of the reagents and temperature (Scheme 8). Thus, at room temperature compound D undergoes a reaction with three molar equivalents of phenyl isothiocyanate that, following desulfurization, affords 3-phenyl-2-phenylimino-2,6,7,8-tetrahydroimidazo[1,2-a] [1,3,5]triazine-4(3H)-thione (20) as the sole product [31]. However, a tandem nucleophilic addition-electrophilic amination reaction takes place when D is treated with aryl isothiocyanates at 40°C; 6,7-dihydro-5H-imidazo[2,1-c] [1,2,4]thiadiazole (21) is formed in case of 4-methylphenyl isothiocyanate, and 7-substituted derivatives 22 and 23 are obtained in the case of more reactive phenyl and p-chlorophenyl isocyanates [35].…”

“…As depicted in Scheme 10, treatment of D″ with p-tolylsulfonyl isocyanate at room temperature or heating at 80°C with corresponding arylsulfonyl carbamoylides furnishes 2-(arylsulfonyl)-6,7-dihydro-2H-imidazo[2,1-c][1,2,4]triazol-3(5H)-ones 28-33 in 23-69% of isolated yield [35]. Apparently, the initially formed sulfonylureas are stronger NH acids than the It is worth noting that the pyridine or isoquinoline formimidates and formamidines react with HOSA in the presence of pyridine to give [1,2,4]triazolo[1,5-a]pyridine or [1,2,4]triazolo[5,1-a]isoquinoline, respectively [55], via the tandem nucleophilic substitution-electrophilic amination reaction. Another variant of N-N bond formation consists of the treatment of 4-aminopyrimidine-5-carbaldehydes with HOSA.…”

“…The reaction of aryl amidate anion K has a lowest barrier (11.1 kcal/mol) and is considerably more exothermic (59.5 kcal/mol) than the corresponding reaction of aryl thioamidate J (36.8 kcal/mol) and especially arylsulfonyl amidate anion M (19.6 kcal/mol). The results presented above prompted us to develop a new synthetic method for the preparation of bicyclic imidazo [2,1-c] [1,2,4]triazole derivatives incorporating the N-N + bond. We found that the reaction of hydroxylamine-O-sulfonate D with Eschenmoser's salt in a 2:1 molar ratio carried out in anhydrous DMF in the presence of triethylamine gives rise to the formation of 2,2-dimethyl-3,5,6,7-tetrahydro-2H-imidazo[2,1-c][1,2,4]triazol-2-ium 2-hydroxylimino-imidazolidine-O-sulfonate (34) in 64% yield (Scheme 11) [67].…”

“…O-Substituted hydroxylamine derivatives have been extensively reviewed [1][2][3] and compounds with N-O linkage constitute a vital group of chemical reagents, which incorporate either the nucleophilic or electrophilic nitrogen atom. Thus, the O-substituted nitrogen atom may retain its natural nucleophilic amine reactivity ( σ-NH-O-R σ+ ), and such compounds are used for the synthesis of N-hydroxyamides [4], N-hydroxypeptides [5], N-hydroxy β-lactams [6], hydroxamic acids [7], N-hydroxyimides [8], oximes [9], nitrones [10], isoxazoles [11], nitriles [12], amides [13], and can be applied to α-acyloxylation of aldehydes and ketones [14].…”