An Improved Synthesis of 3,6-Dihydro-as-indacene,Synthesis

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An Improved Synthesis of 3,6-Dihydro-as-indacene
Synthesis ( IF 2.2 ) Pub Date : 2020-09-02 , DOI: 10.1055/s-0040-1707372
Marcelo Preite ₁ , Elies Molins ₂ , Ivonne Chávez ₃ , Mungalimane K. Amshumali ₄ , Cesar Morales-Verdejo ₅ , Yuvaraja Dibdalli _{3,

4} , Rodrigo Faúndez ₃ , Juan M. Manriquez ₃

Affiliation

Abstract

This contribution describes an updated synthetic route to 3,6-dihydro-as-indacene along with full characterization of all intermediates. The title compound is prepared by Mannich condensation of 2-methylfuran with formaldehyde and dimethylamine hydrochloride, quaternization of the resulting amine with methyl iodide, and conversion into the ammonium hydroxide salt by treatment with silver oxide in water. Subsequent Hoffmann elimination and [6,6]-cycloaddition through pyrolysis produces a furanocyclophane, which after photooxidation, intramolecular cycloaddition, and dehydration with sodium carbonate affords 2,3,6,7-tetrahydro-1,8-dione-as-indacene. Reduction of this diketone gives a mixture of alcohols, which after dehydration under slightly basic or acidic conditions produces 3,6-dihydro-as-indacene. The structure is confirmed by X-ray diffraction, and all intermediates are characterized by means of ¹H and ¹³C NMR spectroscopy.

Publication History

Received: 11 June 2020

Accepted after revision: 11 August 2020

Publication Date:
02 September 2020 (online)

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

中文翻译：

改进的3,6-二氢-茚并茚合成

摘要

该文献描述了更新的合成路线，即以3,6-二氢为茚并二苯以及所有中间体的完整表征。通过2-甲基呋喃与甲醛和二甲胺盐酸盐的曼尼希缩合，将所得胺与碘甲烷季铵化，然后通过在水中用氧化银处理将其转化为氢氧化铵盐，来制备标题化合物。随后的霍夫曼消除和[6,6] -环通过热解产生furanocyclophane，该光氧化，分子内环加成，和脱水用碳酸钠后，得到2,3,6,7-四氢-1,8-二氮杂dione-作为-茚并四烯。还原该二酮得到醇的混合物，其在弱碱性或酸性条件下脱水后，生成3,6-二氢-吲哚并烯。该结构通过X射线衍射确认，并且所有中间体通过¹ H和¹³ C NMR光谱表征。