Synthesis and spectroscopic characterization of 5-diaminomethylidene barbiturates

Abstract

A reação de aminas com ditiocicloexilidenos é uma reação geral para a síntese de diaminometilenobarbituratos. Quando diaminas do tipo H 2 N-(CH 2 ) n -NH 2 são utilizadas como nucleófilos os produtos majoritários de reação são compostos bicíclicos, cujos rendimentos aumentam conforme n diminui, n = 2, 3, 4. Quando n = 6, obtém-se altos rendimentos (80-90%) de novos compostos macrocíclicos de 18 e 27 membros. As atribuições dos deslocamentos químicos de 1 H e 13 C RMN de todos os produtos são discutidas.The reaction of amines with dithiocyclohexylidenes is a general reaction for the synthesis of diaminomethylidene barbiturates. When diamines of the type H 2 N-(CH 2 ) n -NH 2 are used as nucleophiles bicyclic compounds are the major reaction products, with yields increasing as n decreases, n = 2, 3, 4. When n = 6, macrocyclic compounds, novel 18 and 27 member rings, are obtained in very good yields. The 1 H and 13 C NMR assignment for all products is discussed.

Synthesis and mechanism of formation of oxadeazaflavines by microwave thermal cyclization of ortho-halobenzylidene barbiturates

“…17 The draw of this last method is the need for relatively long reaction times at high temperatures, for example 1.5 hours at 260 °C, affording oxadeazaflavines in medium to low yields (50% or lower). On the other hand, because benzylidene barbiturates are easy to prepare by reaction of benzaldehydes with barbituric acid [17][18][19][20] and have been used as starting materials for different reactions, [21][22][23][24][25][26][27][28] the optimization of the second reaction method is important.…”

“…2102 for relatively long reaction times at high temperatures, for example 1.5 hours at 260 °C, affording oxadeazaflavines in medium to low yields (50% or lower). On the other hand, because benzylidene barbiturates are easy to prepare by reaction of benzaldehydes with barbituric acid [17][18][19][20] and have been used as starting materials for different reactions, [21][22][23][24][25][26][27][28] the optimization of the second reaction method is important.One important procedure to improve reactions and decrease their environmental impact is the exclusion of solvents in combination with the use of microwave irradiation. [29][30][31][32][33][34][35] The use of microwaves has an important effect to improve yields and reduce reaction times.…”