Enantioselective ethylation of aldehydes with 1,3-N-donor ligands derived from (+)-camphoric acid

Development of polymer-supported chiral aminoalcohols derived from biomass and their application to asymmetric alkylation

“…The formation of benzyl alcohol has been observed by others and is attributed to a secondary process in which benzaldehyde is reduced by the zinc alkoxide of the ethylation product, 1-phenyl-1-propanoxide. 16 All the reactions tested gave the (R)-1-aryl-1-propanol as major enantiomer. Comparison of the inductive capacity between all evaluated chiral ligands indicates that 8a, bearing a tertiary amino group, is the most efficient (entry 3, Table 1).…”

“…8b Simultaneously, this reaction leads to the generation of optically active secondary alcohols with relevant industrial application such as drug candidates, agrochemicals, perfumes, and several other high added value intermediates. 16 To perform the reaction, the solid-supported aminoalcohol 8ad was suspended in a minimum amount of dry toluene at 0°C and a 1.1 M solution of ZnEt 2 in toluene was added. After stirring for 160 30 min, the mixture is allowed to reach room temperature, the corresponding aldehyde (1 mmol) was added and stirring of the reaction was continued for 22-66 h. The suspension was filtered to recover the immobilized ligand, the solution obtained was passed through a pad of silica gel or celite and the filtrate evaporated under reduced pressure to give the corresponding 1-aryl-1propanol.…”

d-Penicillamine and l-cysteine derived thiazolidine catalysts: an efficient approach to both enantiomers of secondary alcohols

“…In continuation of our studies on the enantioselective alkylation of aldehydes, [24][25][26][27][28] we undertook the synthesis of D-penicillamine derived thiazolidines 2a-c and subsequently tested them in the enantioselective alkylation of benzaldehyde with diethylzinc. Simultaneously, we synthesized structurally analogous L-cysteinederived thiazolidines 1a-c in order to analyze the effect of the chiral center and of the steric hindrance on the selectivity of the alkylation products.…”

Synthesis and catalytic application of ferrocene substituted camphane-based aminoalcohols and S-containing heterocyclic analogues

“…The realization of diverse substitutions at the 1-, 2-, 3-and 7-positions of the camphane skeleton has been achieved by introducing mainly hydroxy and/or heteroatom-containing groups ( Fig.1; the methyl groups in the product representing the different substitutions are omitted for clarity). Several synthetic strategies have been developed for the introduction of functionalities at 1-and 2position of the bicyclic skeleton, [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] some of which include skeleton rearrangements. [33][34][35][36][37] The most simple way to introduce simultaneously hydroxyl-and heteroatom-containing groups at the 2-position is the nucleophilic addition of functionalized organometallic reagents to camphor and fenchone leading directly [38][39][40][41][42][43][44][45][46][47] or after subsequent transformations [48][49][50][51] to aminoalcohols or analogues.…”