(−)-Sparteine-Mediated α-Lithiation of N-Boc-N-(p-methoxyphenyl)benzylamine:  Enantioselective Syntheses of (S) and (R) Mono- and Disubstituted N-Boc-benzylamines

The Chemistry of Vicinal Diamines

“…[190] They showed that the reaction of 428 with n-butyllithium in toluene, in the presence of (À)-sparteine, followed by addition to N-benzylideneaniline (432) yielded trans-imidazolidinone (R,R)-433 as the major adduct with a 73 % enantiomeric excess. …”

Synthesis of Highly Enantio-Enriched α-Amino Acids by Carboxylation ofN-(α-Lithioalkyl)oxazolidinones

“…Scheme 1 As previously reported, [7] the α-amino lithio derivative was selected since it can be obtained either by direct deprotonation of nitrogen precursors of the amino group (for example isocyanide 2) [10] or by heteroatom to lithium exchange using principally α-aminostannanes. The enantioselective deprotonation of 2 by nBuLi/sparteine [11] being completely unsuccessful, the tin-lithium exchange was used, taking advantage of the results of Pearson et al [12] who obtained diverse amino derivatives with good diastereoselectivity using organolithium species obtained from enantiopure oxazolidinones 1. [13] The required compounds 1aa and 1ab (1:1 mixture of diastereomers) were prepared as depicted in Scheme 2 from 3-methylthiopropanal.…”

Reagent-Controlled Lithiation–Borylation

“…A few examples involving α-N-stabilized organolithiums have been described in the literature (Table 10). Beak's lithiated N-Boc-pyrrolidine 87 [53], indoline 88 [54], and benzyl amine 89 [55] reacted well with boranes to give various intermediate boronate complexes 90, 91, and 92. In these cases the strong Lewis acid TMS-OTf was required in order to trigger the more challenging 1,2-migrations.…”