In situ DRIFTS study on the synthesis of N -alkylmorpholines
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In situ DRIFTS study on the synthesis of N-alkylmorpholines Chenxi Luo • Hu Luo • Chao Qian • Yunbin Chen Lie Feng • Xinzhi Chen
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Received: 4 May 2012 / Accepted: 31 August 2012 / Published online: 18 September 2012 Ó Springer Science+Business Media B.V. 2012
Abstract In situ diffuse reflectance Fourier-transform infrared spectroscopy was used to perform mechanistic investigation on the synthesis of N-alkylmorpholines from diethylene glycol (DEG), alcohol and ammonia. The results showed that the synthesis of N-alkylmorpholines on a heterogeneous catalyst proceeded along the reaction path between DEG and alkylamine when choosing CuO–NiO/c-Al2O3 as a suitable catalyst. In addition, the yield of methylmorpholine and ethylmorpholine was 86.4 and 76.6 %, respectively. Keywords
In situ DRIFTS N-alkylmorpholines Mechanism Synthesis
Introduction N-Alkylmorpholines play an important role in the production of many chemical compounds including surfactants, dyes, pesticides, preservatives, herbicides, rubber accelerator, lubricants and medicinal intermediates [1–3]. For example, N-alkylmorpholines can be used as important blocks in many pharmaceutical compounds such as moclobemide for depression, fominoben for antitussive, morphocycline for infection and the diagnosis of lung cancer, bimolane for psoriasis, and so on (Fig. 1). Given its versatility, exploring more efficient synthesis of N-alkylmorpholines is still attracting much attention [4, 5]. There are two main methods of synthesizing N-alkylmorpholine. A traditional method is substitution on morpholine with alkyl halides, which is efficient but C. Luo H. Luo C. Qian X. Chen (&) Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China e-mail: [email protected]; [email protected] Y. Chen L. Feng Zhejiang Jianye Chemical Co., Ltd., Jiande 311600, People’s Republic of China
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C. Luo et al. Cl O
O OH N N H
Cl
HO O O
HN
O
N
O
H
N
OH
O H N
N
OH
N
O
N O
N
HO HN
O N
O
O
N
O
N O
moclobemide
fominoben
morphocycline
bimolane
Fig. 1 N-Alkylmorpholines used as important blocks in pharmaceutical compounds
limited by involving mutagenic halides and much effluent. Moreover, polyalkylation decreases the selectivity [6]. In response, metal-catalysed alkylation of amines with alcohols was developed recently, which employs DEG, alcohol and ammonia as the starting materials. Although the mechanism of synthesis of morpholine(III) has been reported, the mechanism of synthesis of N-alkylmorpholines remains unknown [7, 8]. Considering that the monoalkylated products can be obtained with high selectivity and that the approach is of less pollution [9], investigation on the mechanism of synthesis of N-alkylmorpholines from alcohol, ammonia and DEG is of significant importance. In this work, CuO–NiO/c-Al2O3 [10, 11] was used as catalyst, and a mechanism of synthesizing N-alkylmorpholines was proposed on referring previous mechanism of synthesis of morpholine through the study of the me
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