Acyl derivatives of cyclic secondary amines. Part 1. Dipole stabilization of anions: the cumulative effect of two stabilizing groups

Abstract

Lithiation studies with diacylimidazolidines, diacylhexahydropyrimidines, and triacylhexahydro-I ,3,5triazines indicate that no substantial increase in carbanion stability occurs as a result of the introduction of the second stabilizing group. Relative energies are calculated for three conformers of lithiated diformylimidazolidine, six conformers of lithiated diformylhexahydropyrimidine, and eight conformers of lithiated triformylhexahydro-sym-triazine. For the six-membered rings, conformers with equatorial lithium are always more stable those those with axial lithium. Although equatorial syn-syn conformers (with double 0-Li co-ordination) are more stable than equatorial syn-anti, the difference is significantly less than that found between the corresponding syn-anti and (least stable) anti-anti conformers.The concept of dipole stabilization of carbanions is well recognized, and dipole-stabilized anions of type R1R2C---NR3 -

Design, Synthesis, and SAR of Novel 1,3-Disubstituted Imidazolidine or Hexahydropyrimidine Derivatives as Herbicide Safeners

“…Diamine (5 mmol) and formaldehyde (5 mmol; 37% (v/v) solution) were added to water (20 mL). The reaction mixture was stirred at 100 °C for 0.5–2 h and the key intermediates imidazolidine and hexahydropyrimidine were obtained …”

Carbon‐metalated triazines and tetrazines: Synthesis and reactivity

“…[51] S C H E M E 2 7 Preparation of 2,4,6-tri-carboranyl- 166 did not react with dimsyl sodium, but could be transformed into C-deuterated derivatives 167 by treatment with LDA and D 2 O (Scheme 35). [52] Relative energies of the lithiated triformyltriazine conformers were also calculated and compared with the lithiated imidazolidine and pyrimidine analogs. [52] Deprotonation of 1,3,5-trimethyl-1,3,5-triazacyclohexane (168), regardless on the reaction conditions, gave the product of lithiation at the methylene unit 169 (Scheme 36).…”

“…[52] Relative energies of the lithiated triformyltriazine conformers were also calculated and compared with the lithiated imidazolidine and pyrimidine analogs. [52] Deprotonation of 1,3,5-trimethyl-1,3,5-triazacyclohexane (168), regardless on the reaction conditions, gave the product of lithiation at the methylene unit 169 (Scheme 36). [53] Reaction of the latter with carbonyl compounds afforded the expected saturated triazine addition products 170, which could be hydrolyzed to give α-hydroxy aldehydes 171.…”

Preparation of diamines by lithiation–substitution of imidazolidines and pyrimidines

“…5 This chemistry provided a new acyl anion equivalent, although the stabilization of the intermediate organolithium species afforded by the second N-Boc group was not Scheme 1 thought to be significant. 6 Therefore, we were interested in studying unsymmetrical imidazolidines in which a Boc group is attached to only one of the two nitrogen atoms. Seebach and co-workers have reported one such approach (Scheme 3), in which deprotonation of the imidazolidine 4 occurs on treatment with tert-BuLi to give, after electrophilic quench, the diastereomerically pure derivatives 5.…”