Synthesis of Tetrahydroindole Derivatives via Metal-Free Intramolecular [4+2] Annulation of Ynamides

doi:10.6023/cjoc202201006

Chinese Journal of Organic Chemistry ›› 2022, Vol. 42 ›› Issue (5): 1501-1508.DOI: 10.6023/cjoc202201006 Previous Articles Next Articles

ARTICLES

无金属催化炔酰胺分子内[4+2]环化反应合成四氢吲哚衍生物

张智鑫^a, 翟彤仪^a, 朱伯汉^b, 钱鹏程^b^,^*(), 叶龙武^a^,^c^,^*()

a 厦门大学化学化工学院福建厦门 361005
b 温州大学化学和材料工程学院浙江温州 325035
c 中国科学院上海有机化学研究所金属有机化学国家重点实验室上海 200032

收稿日期:2022-01-05 修回日期:2022-01-24 发布日期:2022-01-27
通讯作者: 钱鹏程, 叶龙武
作者简介:
^†共同第一作者
基金资助:
国家自然科学基金(21772161)

Synthesis of Tetrahydroindole Derivatives via Metal-Free Intramolecular [4+2] Annulation of Ynamides

Zhixin Zhang^a, Tongyi Zhai^a, Bohan Zhu^b, Pengcheng Qian^b(), Longwu Ye^a^,^c()

a College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005
b College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035
c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032

Received:2022-01-05 Revised:2022-01-24 Published:2022-01-27
Contact: Pengcheng Qian, Longwu Ye
About author:
^†These authors contributed equally to this work
Supported by:
National Natural Science Foundation of China(21772161)

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Abstract

A metal-free reaction of 4-siloxy-3,5-diene ynamides via an intramolecular [4+2] annulation has been developed. In the presence of catalytic Et₃N, this protocol leads to the facile formation of six-membered cycloadducts. This reaction can proceed smoothly under mild condition without transition-metal-catalysts and its substrate scope is wide. This strategy provides a concise and practical protocol to synthesize natural product and bioactive compounds containing 4-hydroxyl hydroindole skeletons.

Key words: annulation reaction, metal-free catalysis, ynamides, heterocycle synthesis

Cite this article

Zhixin Zhang, Tongyi Zhai, Bohan Zhu, Pengcheng Qian, Longwu Ye. Synthesis of Tetrahydroindole Derivatives via Metal-Free Intramolecular [4+2] Annulation of Ynamides[J]. Chinese Journal of Organic Chemistry, 2022, 42(5): 1501-1508.

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Fig. & Tab. 6

References 11

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Entry	Catalyst	Conditions	Yield^b/%
Entry	Catalyst	Conditions	2a	2aa
1	—	DCE, 80 ℃, 12 h	<5	<5
2	Cu(CH₃CN)₄PF₆	DCE, r.t., 2 h	<5	20
3	Cu(OTf)₂	DCE, r.t., 2 h	<5	15
4	MsOH	DCE, r.t., 0.5 h	<5	22
5	HNTf₂	DCE, r.t., 0.5 h	<5	<5
6^c	TFA	DCE, 80 ℃, 12 h	<5	<5
7	TfOH	DCE, r.t., 0.5 h	<5	<5
8^c	Et₃N	DCE, r.t., 24 h	<5	<1
9	Et₃N	DCE, 80 ℃, 12 h	99	<1
10	Pyrrolidine	DCE, 80 ℃, 12 h	99	<1

Entry	Catalyst	Conditions	Yield^b/%
Entry	Catalyst	Conditions	2a	2aa
1	—	DCE, 80 ℃, 12 h	<5	<5
2	Cu(CH₃CN)₄PF₆	DCE, r.t., 2 h	<5	20
3	Cu(OTf)₂	DCE, r.t., 2 h	<5	15
4	MsOH	DCE, r.t., 0.5 h	<5	22
5	HNTf₂	DCE, r.t., 0.5 h	<5	<5
6^c	TFA	DCE, 80 ℃, 12 h	<5	<5
7	TfOH	DCE, r.t., 0.5 h	<5	<5
8^c	Et₃N	DCE, r.t., 24 h	<5	<1
9	Et₃N	DCE, 80 ℃, 12 h	99	<1
10	Pyrrolidine	DCE, 80 ℃, 12 h	99	<1

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无金属催化炔酰胺分子内[4+2]环化反应合成四氢吲哚衍生物

Synthesis of Tetrahydroindole Derivatives via Metal-Free Intramolecular [4+2] Annulation of Ynamides

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Entry	Yield/%	Entry	Yield/%
1	99	8	88
2	94	9	97
3	94	10	99
4	84	11	88 (1.2∶1 dr)
5	88	12	89
6	72	13	99
7	86

Entry	Yield/%	Entry	Yield/%
1	99	8	88
2	94	9	97
3	94	10	99
4	84	11	88 (1.2∶1 dr)
5	88	12	89
6	72	13	99
7	86