Gold-Catalyzed [5+2]- and [5+1]-Annulations between Ynamides and 1,2-Benzisoxazoles with Ligand-Controlled Chemoselectivity

This work describes two distinct
annulations between ynamides and
1,2-benzisoxazoles with chemoselectivity controlled by ligands. With
IPrAuCl/AgNTf2, aryl-substituted ynamides undergo [5+2]-annulation
reactions, whereas P­(t-Bu)2(o-biphenyl)­AuCl/AgNTf2 alters the chemoselectivity of the
same ynamides to implement [5+1]-annulation reactions. 13C-Labeling experiments confirm
that a 1,2-sulfonamide shift is involved in the [5+1]-annulation process.
A plausible mechanism is postulated to rationalize the mechanisms
of the two annulations.

本研究描述了两种独特的反应，即 ynamides 与 1,2-苯并硫杂唑之间的交联反应，其化学选择性受配体控制。在使用 IPrAuCl/AgNTf2 作为催化剂的情况下，芳基取代的 ynamides 可发生 [5+2] 交联反应；而 P­(t-Bu)2(o-biphenyl)­AuCl/AgNTf2 则改变了相同 ynamides 的化学选择性，以实现 [5+1] 交联反应。13C 标记实验证实，1,2-磺酰胺的位移是 [5+1] 交联过程的关键。为了阐释两种交联反应的机理，提出了一种合理的机制。