芝麻素类型木脂素的合成研究Ⅲ．2—芳基呋喃—3，4—二羧酸二甲酯的合成

本文报道了9个恶二唑类化合物的制备。研究了6个恶唑和恶二唑类化合物与丁炔二酸二甲酯的Diels-Alder反应，其中4个获得了目标产物2－芳基呋喃－3，4－二羟酸二甲酯。

Studies on the Synthesis of Sesamin-Group Lignans III. Preparation of Dimethyl 2-Arylfurane-3, 4-dicarboxylates

Dimethyl 2-arylfurane-3, 4-dicarboxylates (3) were selected as the key intermediates of a synthetic route of sesamin-group lignans designed by us. The Diels-Alder and reverse Diels-Alder reactions between 4, 5-diaryloxazoles (2) and dimethyl acetylene-dicarboxylate and also between 2-aryl-l, 3, 4-oxadiazoles (1) and dimethyl acetylene-dicarboxylate were therefore investigated. The results obtained and the reaction conditions taken on trial were summarized in Tables 2, 3 and 4.A study on the preparation of 4, 5-diaryloxazoles (2) was reported in the 2nd paper of this research series. And the 2-aryl-l, 3, 4-oxadiazoles (1) were prepared by a two-step process.The benzohydrazide (6) was prepared by the reaction of ethyl benzoates with hydrazine, and then nine 2-aryl-l, 3, 4-oxadiazoles (Ja-i) were obtained by the reaction of 6a-i with triethyl orthoformate. Three of the oxazoles (2a-c) and three of the oxadiazoles (1a-c) were subjected to the Diels-Alder reaction with dimethyl acetylene-dicarboxylate for the preparation of the desired intermediate dimethyl 2-arylfurane-3, 4-dicarboxylates (3), in which only the reactions of 2a-c and 1a between dimethyl acetylene-dicarboxylate were proceeded and the products (3) produced.