New phosphorus-containing polycycles with a spiroamine group

Abstract

Aim. To synthesize hexahydrospiro[cyclopropane-1,10’-pyrido[1,2-c]quinazoline] and 2-λ5-benzo[f][1,4,2]diazaphosphepine derivatives – new N-P containing heterocyclic compounds with the 6-azaspiro[2.5]octane fragment.Results and discussion. A new analog of the powerful electrophilic reagent – “Alder dimer” ‒ was obtained from the interaction of triflic anhydride and spiro(4-cyclopropane) piperidinyl formamide, and further used to synthesize new Nʹ-PV- and PIII-substituted Νʹ-phenyl, Νʹʹ-hexahydro(azaspiro)octylformamidinium salts – precursors of acyclic N-phosphorylated diamino carbenes with a spiroamine group. It has been shown that acyclic N-phosphorylated diaminocarbenes are transient species affording various products. The structure of the final product is primarily determined by nature of the phosphorus-bearing substituent, namely a phosphoryl or phosphino-group. N-PV-substituted carbene undergoes a 1,2-phosphorus shift with the formation of (selenophosphoryl)formamidine in a high yield. For N-PIII-substituted carbene a compatible 1,3-H shift also occurs with the formation of an intermediate azomethine ylide converted into a new heterocyclic system – hexahydrospirocyclopropane -1,10’-pyrido[1,2-c]quinazoline. Under the action of acid an unexpected further expansion of the 6-member ring occurs with the formation of a diazepine derivative.Experimental part. The reaction of Alder reagent with N-PV-seleno phosphoryl arylamides afforded N-phosphorus substituted formamidinium salts, which are easily reduced to PIII analogues. In addition to the corresponding formamidines, the new N-phosphorylated spiroamine-containing polycyclic system was isolated from the reaction mixture formed by the deprotonation of such salts with a strong non-nucleophilic base.Conclusions. The Alder reagent approach allows synthesizing precursors of acyclic formamidine carbenes with the spiroamine group. Such carbenes are unstable. By converting these compounds N-PIII-substituted tetrahydropyrimidine and diazaphosphepine derivatives with the 6-azaspiro[2.5]octane fragment have been obtained for the first time.