Trichlorosilyl triflate-mediated enantioselective directed cross-aldol reaction between ketones using a chiral phosphine oxide as an organocatalyst

Abstract

Trichlorosilyl triflate-promoted directed cross-aldol reaction between ketones in the presence of a chiral phosphine oxide as an organocatalyst is described. This is the first enantioselective cross-aldol reaction between simple ketones with good enantioselectivity.

Cu‐Catalyzed Asymmetric Allylic Alkylation of Phosphonates and Phosphine Oxides with Grignard Reagents

“…For example, phosphonates and phosphonic acids can act as isosteres of carboxylic esters and acids, which improves their activity or bioavailability; in addition, they have also been used as nonhydrolyzable phosphate mimics 5. In addition, phosphine oxides are key components in Wittig‐type reactions,6 ligands or organocatalysts in asymmetric synthesis,7 and stereogenic precursors to their corresponding phosphines 8…”

Titanium‐Catalyzed Hydroalumination of Conjugated Dienes: Access to Fulvene‐Derived Allylaluminium Reagents and Their Diastereoselective Reactions with Carbonyl Compounds

“…This approach, involving fulvene‐derived allylaluminium species, is of particular interest since it constitutes an alternative to cyclopentanone–ketone cross‐aldol reactions 13. The corresponding products can be readily obtained in two steps from the homoallylic alcohol: hydrogenation of the endocyclic double bond followed by oxidative cleavage of the exocyclic double bond (Scheme ).…”

“…The reaction was continued for 5 h. The reaction mixture was diluted with water (10 mL) and extracted with CH 2 Cl 2 (3×15 mL). The organic layer was evaporated to dryness and the residue was purified by column chromatography to give the ketone 6 b (142 mg, 70 %) as a colourless oil 13 . 1 H NMR (250 MHz, CDCl 3 , 25 °C, TMS): δ =7.46 (m, 2 H), 7.34 (m, 2 H), 7.25 (m, 1 H), 4.58 (br s, 1 H),2.44 (m, 2 H), 2.16 (m, 1 H), 1.82 (m, 1 H), 1.67 (m, 2 H),1.58 ppm (s, 3 H); 13 C NMR (62.5 MHz, CDCl 3 , 25 °C, TMS): δ =222.41, 145.9, 128.10, 127.00, 125.16, 74.97, 59.90, 39.89, 27.13, 23.54, 20.00 ppm; HRMS‐ESI: m / z : elemental analysis calcd (%) for C 13 H 16 NaO 2 : 227.1048; found: 227.1050 [ M +Na] + .…”

Enantiomerically Pure Bithiophene Diphosphine Oxides as Catalysts for Direct Double Aldol Reactions

“…[1][2][3] Seminal works by Denmark and colleagues [4][5][6] with chiral phosphoroamides have shown the versatility of the catalytic system that opened avenues to several different synthetic applications. 7 Soon after, Nakajima and colleagues [8][9][10][11][12][13][14] and we [15][16][17] demonstrated that phosphine oxides could also coordinate SiCl 4 and generate hypervalent cationic silicon species in situ as chiral Lewis acids able to promote stereoselective direct aldol reactions.…”