Synthesis and reactivity of dipole-stabilized but unchelated alpha-aminoorganolithiums

Two N-methyl-5-lithio-2-pyrrolidinones have been prepared by tin-lithium ex change. These two alpha-aminoorganolithium compounds that are stabilized by an amide dipole, but not by chelation to the amide carbonyl. Both constitu te test cases for comparing the stability and reactivity of "dipole-stabili zed" and "unstabilized" alpha-aminoorganolithiums. We find that active meth ylene protons interfere with the reaction, so geminal disubstitution a to t he amide carbonyl was necessary to supress side reactions. These species do not react as efficiently as unstabilized alpha-aminoorganolithiums, or eve n as well as chelated dipole-stabilized a-aminoorganolithiums, toward typic al electrophiles. The tin-lithium exchange to form these species was also n ot as facile as with other alpha-aminoorganostannanes.