Asymmetric nucleophilic acylation via metalated .alpha.-aminonitriles possessing an axially disymmetric tertiary amino group

Efficient, Rhodium‐Catalyzed Hydrogenation of α‐Dehydroamino Acid Esters with Chiral Monodentate Aminophosphanes Bearing Two Binaphthyl Groups

“…[22] Interestingly, the counterparts of the two above ligands, namely (S aze ,S bin )-4a and (R aze ,R bin )-4b gave poorer results (up to 20 % decrease) whatever the substrates used ( Table 2, entries [12][13][14][15][16][17][18][19]. Switching the chiral configuration of the azepine moiety from R, as in (R aze ,S bin )-4c, to S, as in (S aze ,S bin )-4a, clearly led to a significant drop of enantioselectivity ( Table 1, entry 1 and Table 2, entries 5-7 and 16-19; compare also with the results obtained for MonoPhos, Table 2, entries [21][22][23][24]. Such a match and mismatch effect between diastereoisomeric pairs has already been reported for other phosphoramidites containing two stereogenic centres but not to such an extent.…”

“…Regardless of the unsaturated substrate used, ee values higher than 99 % were obtained with enantiomeric phosphoramidites (R aze ,S bin )-4c and (S aze ,R bin )-4d, which is well above the values reported for Feringa's MonoPhos ligand, (binoP)NMe 2 ( Table 1, entry 1 and Table 2, entries 5-7, [21][22][23][24]. These findings contrast with the results of de Vries et al, who showed that replacing the amino group of Mon-oPhos by some seven-membered, cyclic amino groups decreases the enantioselectivity.…”

“…The new ligands were assessed in the rhodium-catalyzed hydrogenation of α-dehydroamino acid esters. It is noteworthy that ammonium salts derived from binaphthyl-based azepine derivatives [23,24] have already been successfully employed as chiral phase-transfer catalysts. [25,26] To date, only one phosphoramidite containing an azepinyl moiety has been reported.…”

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

“…Chiralf ormamides [9] needed foro ur projectw ere easily prepared from chiral secondary amines,b yr eaction with formic acetic anhydride [9a, 10] providing an initial selection of chiral formamidesi nexcellent yields ( Table 1, 3a-w to 4a-w). Not all the required secondary amines were commercially available, so additional examples were prepared from chiral primary amines by reductive amination of aldehydes [11] or ketones [12] (Table 1, except 3a,b,d,g which werep urchased, and 3c, [13] 3g [14] which were synthesised by other means).…”

“…Comparing the 9-anthracenylmethylformamide 4n which performed very poorly,g iving 6 in only 3% ee ( Table 2, entry 15), and the corresponding 1-naphthylmethyl analogue 4j,w hich was one of the best chiral formamides( 40 % ee, Ta ble 2, entry 11)s uggests that with anaphthalene substituent, the steric bias is offset from the point of attachment to the centre of the formamides tructure, but an anthracene attached at C-9 is too symmetrical (see Figure 1a nd Supporting Information). c -9 9 [13] d Me Ph HP h-9 9 [a] e Ph Et H 63 79…”