syn-Selective aldol reaction of propynal–hexacarbonylcobalt complexes with ketene silyl acetals

Abstract

Phenylpropynal-hexacarbonylcobalt complex, prepared from 3-phenylpropynal with octacarbonylcobalt, afforded on treatment with the seven-membered ketene trimethylsilyl acetal the syn-aldol product in a highly stereoselective manner. Similar exposure of the above complex to the six-and five-membered ketene trimethylsilyl acetal gave the corresponding syn-aldol products predominantly. The aldol reaction of the cobalt complexes derived from 3-trimethylsilyl-and 3-butyl-propynal with those cyclic ketene silyl acetals proceeded syn-selectively to provide the syn-aldol products. The preferential formation of the syn-over the anti-isomers was also achieved in the reaction of the cobalt complexed 3-trimethylsilylpropynal with acyclic ketene trimethylsilyl acetals, derived from methyl or tert-butyl propionate. In contrast, uncomplexed 3-phenyl-, 3-trimethylsilyl-and 3butylpropynal furnished the corresponding aldol products nonselectively or anti-isomers predominantly depending on the structure of the starting ketene trimethylsilyl acetal.Paper 1/03005A

Nicholas Reactions of Pentadiynyl–Co2(CO)6 Cations. Synthesis of Antimalarial Hinokiresinol Analogues

“…1 H NMR (500 MHz, CDCl3):  = δ 2.49 (s, 3H), 0.35 (s, 9H). 13 C NMR (125 MHz, CDCl3):  = 199. 3, 198.8, 100.2, 80.6, 31.3, 0.6. HRMS (APCI) m/e for C13H12Co2O7 Si [M+H] + calcd.…”

“…1 H NMR (500 MHz, CDCl3):  = 5.31 (dt,J = 6.8,1.8 Hz,1H),2.25 (d,J = 6.8 Hz,1H),2.20 (td,J = 7.3,1.8 Hz,2H),1.48 (m,2H), 1.39 (m, 2H), 0.90 (t, J = 7.3 Hz, 3H), 0.33 (s, 9H). 13 C NMR (125 MHz, CDCl3):  = 199.9, 113.5,86.8,80.2,78.3,63.5,30.2,22.0,18.3,13.5,0.5. HRMS (ESI) m/e for C18H20Co2O7Si [M-H] ͞ ; calcd, 492.9570; found, 492.9573.…”

“…1 H NMR (300 MHz, CDCl3):  = 5.55 (dd, J = 6.9, 2.1 Hz, 1H), 2.64 (d, J = 2.1 Hz, 1H), 2.39 (d, J = 6.9 Hz, 1H), 0.34 (s, 9H). 13 C NMR (75 MHz, CDCl3):  = 199.7, 111.2, 83.3, 78.5, 74.1, 63.1, 0.45. 436.8944; found, 436.8963.…”

“…1 H NMR (500 MHz, CDCl3):  = 2.33 (s, 1H), 1.81 (s, 3H), 0.36 (s, 3H), 0.15 (s, 3H). 13 C NMR (125 MHz, CDCl3):  = 200. 0, 118.1, 108.5, 88.3, 78.3, 69.3, 33.5, 0.7, -0.5.…”

“…Hz, 1H), 3.81 (m, 1H), 2.52 (m, 1H), 2.44 (m, 1H), 2.17 (dd, J = 7.1, 2.1 Hz, 2H) 1.46 (m, 2H), 1.40 (m, 2H) 0.90 (t, J = 7.3 Hz, 3H), 0.33 (s, 9H). 13 C NMR (125 MHz, CDCl3):  = 200.2, 135. 6, 117.1, 115.1, 83.9, 81.0, 79.3, 43.1, 37.4, 30.6, 22.0, 18.4, 13.5, 0.7; HRMS (APCI) m/e for C21H22Co2O6Si [M+H] + 516.9922, found 516.9908.…”