Cyclization of Ynamide‐Tethered 1, 3, 8‐Triynes. Issue 34 (29th May 2017)

• Record Type: Journal Article
• Authors: Sabbasani, Venkata R.; Lee, Hyunjin; Xie, Peipei; Xia, Yuanzhi; Lee, Daesung
• Is Part Of: Chemistry. Volume 23:Issue 34(2017)
• Page Start: 8161
• Page End: 8165
• Publication Date: 2017-05-29
• Subjects: 1, 3-diyne -- cyclization -- hydride transfer -- keteniminium -- pyranopyridine -- ynamide; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201701781
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A facile thermal cyclization of ynamide‐tethered 1, 3, 8‐triynes to form a 3, 5, 6, 7‐tetrahydro‐1 H ‐pyrano[3, 4‐ c ]pyridine skeleton is described. Although the mechanism of this unusual reaction has yet to be defined, the formation of either a strained keteniminium or a biradical intermediate followed by a 1, 5‐hydride or ‐hydrogen shift is tentatively proposed as the key elementary steps in the reaction sequence. Appropriate electronic activation at the carbon center donating a hydride or hydrogen is crucial for successful cyclization. Abstract : Zwitterionic or biradical : Thermal activation of ynamide‐tethered 1, 3, 8‐triynes induces a ring‐closure to form a 3, 5, 6, 7‐tetrahydro‐1 H ‐pyrano[3, 4‐ c ]pyridine skeleton. A strained keteniminium or a biradical formation followed a 1, 5‐hydride or a hydrogen shift are the key elementary steps. An appropriate electronic activation at the hydrogen‐ or hydride‐donating carbon, which leads to a stabilized oxonium or a radical species, is crucial for effective cyclization.