Abstract
Multi-component reactions (MCRs) played an important role to produce complex molecular structures in a one-step process. Among all MCRs reported, Biginelli reaction was one of the most well-known and used in organic synthesis to constitute pyrimidine scaffolds. Therefore, a solvent-free Biginelli reaction of 2-aminothiazole, benzaldehyde and ethyl acetoacetate catalyzed by Amberlyst-15 (A-15) had attracted us to pay attention and to do research in order to highly obtain a desired product, a frame of thiazolo[3,2-a]pyrimidine being present in many active biological compounds. Amberlyst-15, polystyrene resin regarded as a green acidic solid, available commercial, inexpensive and reusable catalyst had been firstly and successfully developed for solvent-free Biginelli reaction under ultrasound irradiation to form thiazolo[3,2-a]pyrimidine. Most factors which had influenced on the reaction conversion and yield such as the molar ratios between 2-aminothiazole, benzaldehyde and ethyl acetoacetate, the amounts of catalyst A-15, and reaction time had been investigated. Consequently, the yield of ethyl 7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate had been also found to depend on the amount of the acidic solid catalyst and little excess amounts of the two reactants, e.g. 2-aminothiazole and ethyl acetoacetate. The maximum yield has been obtained 76% after six-hour ultrasound irradiation at 80oC with the molar ratio of 2-aminothiazole : benzaldehyde : ethyl acetoacetate (1.4:1.0:1.4) and 50 mg of catalyst A-15. The results showed that Amberlyst-15 had high capability of recovery and recycling owing to the inconsiderably changes of product yields after two recycle runs.
Highlights
The results showed that Amberlyst-15 had high capability of recovery and recycling owing to the inconsiderably changes of product yield after two recycle runs
Science & Technology Development Journal – Natural Sciences, 4(3):652659 Open Access Full Text Article
Summary
Bức xạ siêu âm hỗ trợ tổng hợp không dung môi hợp chất ethyl 7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate qua phản ứng Biginelli sử dụng xúc tác Amberlyst-15. Phản ứng Biginelli không dung môi giữa 2-aminothiazole, benzaldehyde và ethyl acetoacetate với xúc tác acid Brønsted rắn Amberlyst-15 được quan tâm và nghiên cứu để tạo ra sản phẩm có khung thiazolo[3,2-a]pyrimidine, một trong những khung có mặt trong một số hợp chất có hoạt tính sinh học. Amberlyst-15 (A-15) là một xúc tác rắn xanh, có sẵn trong thương mại, không mắc tiền, có khả năng tái sử dụng cao và lần đầu tiên được sử dụng làm xúc tác cho phản ứng Biginelli không dung môi dưới sự chiếu xạ siêu âm để tạo ra khung thiazolo[3,2-a]pyrimidine. Kết quả cho thấy hiệu suất tạo sản phẩm chính, ethyl 7-methyl5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate phụ thuộc vào lượng xúc tác acid rắn và hai lượng chất phản ứng 2-aminothiazole và ethyl acetoacetate. Từ khoá: không dung môi, Amberlyst-15, chiếu xạ siêu âm, phản ứng Biginelli, thiazolo[3 2-a]pyrimidine
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