One-Pot Synthesis of Spirocyclopenta[a]indene Derivatives via a Cascade Ring Expansion and Intramolecular Friedel–Crafts-Type Cyclization

A one-pot efficient
synthetic approach for the rapid construction
of spirocyclopenta­[a]­indene derivatives has been
developed via an iodine-initiated cascade ring expansion and intramolecular
Friedel–Crafts-type cyclization from propargyl alcohol-tethered
alkylidenecyclobutanes under mild conditions with broad substrate
scope. This cascade process can be elegantly conducted on a gram scale.
A plausible reaction mechanism has been proposed on the basis of a
series of deuterium labeling and control experiments.

一种高效的一步法合成螺环戊并[α] indenene衍生物的方法已被开发，该方法通过碘引发的级联环扩张和分子内Friedel-Crafts型环化反应，从丙炔醇连接的烷基idenecyclobutanes在温和条件下进行，具有广泛的底物适用范围。此级联过程可优雅地在克级规模上实施。基于一系列氘标记和控制实验，已提出一个合理的反应机理。