Visible-light promoted one-pot synthesis of sulfonated spiro[4,5]trienones from propiolamides, anilines and sulfur dioxide under transition metal-free conditions

Abstract

A novel visible-light promoted sulfonylation/ipso-cyclization of N-arylpropiolamides with aromatic amines and DABCO·(SO2)2 to synthesize various sulfonated spiro[4,5]trienones is reported.

Metal Free Sulfonylative Spirocyclization of Alkenyl and Alkynyl Amides via Insertion of Sulfur Dioxide

“…This motivated us to embark upon the current study and herein, we report a unified metal free and mild approach towards the synthesis of both sulfonylated azaspiro [4,5]-decanes (Scheme 1a) and azaspiro [4,5]-trienones (Scheme 1b) with aryl diazonium salts and DABSO. [15] Additionally, a catalyst-free visible light mediated approach was also devised to achieve the aforementioned transformation with diaryliodonium salts (Scheme 1c).…”

Visible‐Light‐Mediated Nitrogen‐Centered Radical Strategy: Preparation of 3‐Acylated Spiro[4,5]trienones

“…Thus, many organic chemists have paied their attention in the development of convenient and efficient strategies for the preparation of spiroquinones, [15–18] especially spiro[4,5]decatrienones [15c–g,16] . The electrophilic ipso ‐cyclization strategies are traditional methods for the construction of substituted spiro[4,5]decatrienones [17d–k,18f−h] . Recently, many chemists, such as Zhang, [15a–d] Zhu, [15e–g] Qiu, [16] Li, [17] Liang, [18a–d] and our group [18e–h] developed many oxidative radical cyclization approaches for the preparation of spiro[4,5]decatrienones.…”

“…The electrophilic ipso ‐cyclization strategies are traditional methods for the construction of substituted spiro[4,5]decatrienones [17d–k,18f−h] . Recently, many chemists, such as Zhang, [15a–d] Zhu, [15e–g] Qiu, [16] Li, [17] Liang, [18a–d] and our group [18e–h] developed many oxidative radical cyclization approaches for the preparation of spiro[4,5]decatrienones. Among these strategies, 3‐acylated spiro[4,5]decatrienones could be prepared by several different pathways, which used aldehydes, [17k] ketoacids, [19] acyl chlorides [18f] as acyl precursors.…”

“…The intermediate D undergoes ipso ‐cyclization to furnish the radical E , which goes through SET to afford the carbocation F under the oxidation of Ir 4+ , regenerating Ir 3+ . The hydroxide ion, which comes from H 2 O under the action RO − , attacks the carbocation F to assemble the intermediate G [17d–k,18f−h] . The intermediate G occurrs release of OMe − and H + to provide the target product 3 aa .…”

Recent Advances in the Construction of Spiro Compounds via Radical Dearomatization

“…In this approach, aryl‐substituted thiols gave 3‐sulfenyl azaspiro[4,5] trienones in moderate to good yields, whereas aliphatic thiols failed. Besides, another two groups independently developed similar protocols to prepare 3‐sulfonated azaspiro[4,5]trienones from N ‐( p ‐methoxyaryl)propiolamides 24 instead of N ‐arylpropiolamides 1 (Scheme 8c–8e) [21i,l] …”