α-Lithioamine synthetic equivalents from dipole-stabilized carbanions: The t-Boc group as an activator for α′-lithiation of carbamates

Asymmetric Deprotonation with Alkyllithium–(−)‐Sparteine

“…However, most of the potential precursors have insufficient acidity. Notable exceptions are those substrates which lead to dipole-stabilized carbanions 29 , among them Oalkyl N,N-dialkylcarbamates 15 10 and N-Boc-(cyclo)alkylamines 18 30 rapid deprotonation is achieved by treatment with s-BuLi/TMEDA in unpolar solvents such as THF, diethyl ether, toluene or pentane at low temperature. The chelate formation in lithium complexes 17 or 20 contributes to stabilization.…”

“…(a) Introduction of a strongly complexing substituent X such as N,N-dialkylcarbamoyloxy by Hoppe and coworkers 208,209 and N-(alkoxycarbonyl)amino groups by Beak and coworkers 30 …”

?-Alkyl-?-aminosilanes: Synthesis via Alkylation and Hydrosilylation

“…Approach V has been exemplified in studies of the metalation chemistry of amine derivatives by Meyers 15 and by Beak. 16,17 Methods related to disconnections II, III, IV and VI have seen little development.…”

“…A type V approach employing metalation of a Boc-derivatized amine followed by reaction with a chlorosilane, largely restricted to secondary amine derivatives, 18 is shown in Eqn [2]. 17 Tertiary amides, both aromatic and aliphatic, are reduced by trichlorosilane with formation of ␣-aminotrichlorosilane products (Eqn [3]). 19 Rearrangement of N-trialkylsilylammonium ylides leads to ␣-amino-␣-cyanotrimethylsilanes.…”

Diastereoselective synthesis of α,α,α′-trisubstituted pyrrolidines and piperidines by directed sequential lithiation/alkylation

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In 1989, Beak disclosed that unsubstituted Boc-protected azaheterocycles may be effectively functionalized at the a-position through a lithiation/alkylation sequence. 19 Several researchers, [20][21][22][23][24][25][26] including one of us, 27,16 have since extended the Beak methodology to include sequential a-functionalizations en route to access a,a-and a,a 0 -disubstituted N-heterocycles, in both racemic and enantioenriched forms. It has been shown that the lithiation of phenyl pyrrolidine S-1 (Fig.…”