85106-98-5Relevant academic research and scientific papers
Lithiation of Bridgehead Position in 3,6-Bridged Piperazine-2,5-diones
Eastwood, Frank W.,Gunawardana, Dionne,Wernert, Gregory T.
, p. 2289 - 2298 (2007/10/02)
2,5-Dimethyl-2,5-diazabicyclooctane-3,6-dione can be lithiated at the 1,4 (bridgehead) positions with 2 equiv. of butyllithium at -78 deg C and deuterated with D2O (D0, 11.2; D1, 56.1; D2, 30.1percent).With butyllithium and methyl iodide the 1,2,5-trimethyl and 1,2,4,5-tetramethyl derivatives are obtained.Treatment of dimethyl 2,6-diaminoheptanedioate dihydrochloride with sodium methoxide in boiling butanol gives 6,8-diazabicyclononane-7,9-dione in 62percent yield.N-Methylation of this compound yields 6,8-dimethyl-6,8-diazabicyclononane-7,9-dione which can similarly be lithiated at the 1,5 (bridgehead) positions and deuterated with D2O (D0, 5.6; D1, 70.8; D2, 23.6percent).Lithiation with butyllithium and reaction with methyl iodide, benzyl iodide or bromomethyl methyl ether gives mono- and di-alkylated products at the 1,5-position.The ability to lithiate the bridgehead positions in these compounds is attributed primarily to a combination of the inductive effect of the carbonyl group and dipole stabilization by the amide nitrogen.
