Study of the bromination of 1,5-dinitro-3-azabicyclo-[3.3.1]non-6-enes

Abstract

Derivatives of azabicyclo[3.3.1]nonane possess various biological activities [1][2][3], consequently broadening the range of compounds of this class is urgent and offers promise for the directed synthesis of biologically active substances and the study of structure-activity relationships. One of the methods of functionalizing the derivatives of 1,5-dinitro-3-azabicyclo[3.3.1]non-6-enes previously synthesized by us [4][5][6][7][8] may be the addition of electrophilic reagents at the double bond. It was shown previously that electrophilic addition of halogenating agents to 2-azanorborn-5-ene leads to the formation of rearranged products [9, 10], and addition of bromine and dihalogen iodates to 2-alkyl-2-azabicyclo[2.2.1]hept-5-ene and 2-alkyl-2-azabicyclo-[2.2.2]oct-5-ene leads to a quaternary ammonium salt containing an aziridinium ring [11,12]. The reactivity of the double bond towards electrophilic interaction in 1,5-dinitro-3-azabicyclo[3.3.1]non-6-enes is reduced due to the influence of the electron-withdrawing 5-NO 2 group. In addition, steric factors characteristic of the framework of the system introduce their own contribution to deactivation. In this connection, as a model permitting study of the reactivity of the C=C double bond of the cyclohexene fragment of the bicyclic system, we selected the bromination reaction which has not been described for compounds of this type up to the present time.It was established that in the reaction of an excess of bromine with 1,5-dinitro-3-azabicyclo[3.3.1]non-6-enes 1a-l in CCl 4 , 3-R-6-bromo-1,5-dinitro-3-azoniatricyclo[3.3.1.0 3,7 ]nonane tribromides 2a-l were isolated in quantitative yield as orange solids readily soluble in water, in place of the expected products of addition of halogen at the double bond, 3-R-6,7-dibromo-1,5-dinitro-3-azabicyclo[3.3.1]nonanes (B). The obtained compounds 2a-l have the structure of quaternary salts and contain the complex tribromide anion,as indicated by __________________________________________________________________________________________