Hsieh Sheng-Hsiang, Chen Chien-An, Chuang Da-Wei, Yang Mao-Chih, Yang Hsu-Tang, Gau Han-Mou
Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan, Republic of China.
Chirality. 2008 Aug;20(8):924-9. doi: 10.1002/chir.20572.
Asymmetric AlPh(3) (THF) additions to a wide variety of aldehydes catalyzed by a titanium catalyst of 20 mol % 1,3-bis[N-sulfonyl-(1R,2S)-1,3-diphenyl-2-aminopropanol]benzene (1) are reported. The catalytic system works excellently for aromatic aldehydes bearing either an electron-donating or an electron-withdrawing substituent on the aromatic ring to afford secondary diaryl alcohols in excellent isolated yields of >or=95% and excellent enantioselectivities of >or=94% ee. The phenyl addition to cinnamaldehyde or 2-furylaldehyde gave corresponding secondary alcohols in 85% and 95% ee, respectively. For aliphatic aldehydes, increasing enantioselectivities of the addition products in terms of increasing steric sizes of aldehydes are observed, and this trend goes from the linear 1-pentanal (87% ee), the secondary cyclohexylaldehyde (95% ee) or the 2-methylpropanal (97% ee), to the tertiary 2,2-dimethylpropanal (99% ee).
报道了由20 mol%的1,3-双[N-磺酰基-(1R,2S)-1,3-二苯基-2-氨基丙醇]苯(1)钛催化剂催化的不对称AlPh(3)(THF)对多种醛的加成反应。该催化体系对芳环上带有供电子或吸电子取代基的芳香醛表现出色，能以大于或等于95%的优异分离产率和大于或等于94% ee的优异对映选择性得到仲二芳基醇。苯基对肉桂醛或2-呋喃醛的加成分别以85%和95% ee的对映选择性得到相应的仲醇。对于脂肪醛，观察到随着醛的空间位阻增大，加成产物的对映选择性增加，这种趋势从直链的1-戊醛(87% ee)、仲环己醛(95% ee)或2-甲基丙醛(97% ee)，到叔丁醛(99% ee)。
