A new copper(I)-tetrahydrosalen-catalyzed asymmetric Henry reaction and its extension to the synthesis of (S)-norphenylephrine |
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Authors: | Xiong Yan Wang Fei Huang Xiao Wen Yuehong Feng Xiaoming |
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Institution: | Key Laboratory of Green Chemistry and Technology (Sichuan University), Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China. |
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Abstract: | A new chiral hydrogenated salen catalyst has been developed for the asymmetric Henry reaction which produces the expected products in moderate to high yields (up to 98 %) with excellent enantioselectivities (up to 96 % ee). A variety of aromatic, heteroaromatic, enal, and aliphatic aldehydes were found to be suitable substrates in the presence of hydrogenated salen 1 f (10 mol %), (CuOTf)(2)C(7)H(8) (5 mol %), and 4 A molecular sieves. This process is air-tolerant and easily manipulated with readily available reagents, and has been successfully extended to the synthesis of (S)-norphenylephrine in 67 % overall yield, starting from commercially available m-hydroxybenzaldehyde. Based on experimental investigations and MM+ calculations, a possible catalytic cycle including a transition state (8 or A) has been proposed to explain the origin of reactivity and asymmetric inductivity. |
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Keywords: | asymmetric catalysis copper Henry reaction norphenylephrine salen |
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