Enantiopure trans-1-amino-2-(arylsulfanyl)cyclohexanes: novel chiral motifs for ligands and organocatalysts
摘要:
In order to obtain the title compounds (1R,2R)-cyclohexane-1,2-diol was stereoselectively converted into cis-(1R,2S)-2-(arylsulfanyl)cyclohexanols and these products were submitted to the nucleophilic substitution via the Mitsunobu reaction (HN3, DEAD). Reduction of the isolated azides gave the desired trans-(1S,2S)-1-amino-2-(arylsulfanyl)cyclohexanes. The (1S,2S)-1-amino-2-(2-aminophenylsulfanyl)cyclohexanes thus prepared were reacted with 3,5-bis(trifluoromethyl)phenyl isothiocyanate to furnish the respective bis-thiourea compounds. An application of a derivative of this type as an organocatalyst (20 mol %) in the Baylis-Hillman reaction gave the respective product in up to 93% ee. (C) 2011 Elsevier Ltd. All rights reserved.
作者:Jian Wang、Hao Li、Xinhong Yu、Liansuo Zu、Wei Wang
DOI:10.1021/ol051822+
日期:2005.9.1
[reaction: see text] A new bifunctional binaphthyl-derived amine thiourea organocatalyst has been developed to promote enantioselective Morita-Baylis-Hillman reaction of cyclohexenone with a wide range of aldehydes. The process, catalyzed by the amine thiourea, affords synthetically valuable chiralallylic alcohol building blocks in high yields and high enantioselectivities.
Asymmetric Morita–Baylis–Hillman reactions of 2-cyclohexen-1-one catalyzed by chiral biaryl-based bis(thiourea) organocatalysts
作者:Yuki Nakayama、Takashi Gotanda、Katsuji Ito
DOI:10.1016/j.tetlet.2011.09.064
日期:2011.11
Newly-developed bis(thiourea) 1d was found to be an efficient organocatalyst for the Morita-Baylis-Hillman reaction. High enantioselectivities were obtained in the reaction of 2-cyclohexen-1-one with both aromatic aldehydes (up to 84% ee) and aliphatic aldehydes (up to 96% ee). (C) 2011 Elsevier Ltd. All rights reserved.
Here, we describe our studies on the thiourea-catalyzed Morita-Baylis-Hillman (MBH) reaction. Chemoselective activation of carbonyl compounds via hydrogen bonding to thiourea as a catalyst is the key to drastic rate acceleration of this reaction. The application of chiral bis-thiourea-type organocatalysts, which can form a chiral double hydrogen-bonding network, is effective for enantioselective MBH reaction. A cooperative system of bis-thiourea compounds, synthesized from 1,2-diaminocyclohexane, and a Lewis base effectively promotes the MBH reaction at lower temperature, affording the MBH adducts in 33-95% yield with 44-90% ee. A plausible transition state model of the enantioselective MBH reaction is presented. (C) 2008 Elsevier Ltd. All rights reserved.