Strain-Release Controlled [4+2+1] Reaction of Cyclopropyl-Capped Diene-Ynes/Diene-enes and CO Catalyzed by Rhodium

06 September 2022, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

ABSTRACT: Achieving transition metal-catalyzed reactions of diene-enes/diene-ynes and carbon monoxide (CO) to deliver [4+2+1] cycloadducts, rather than the kinetically favored [2+2+1] products, is challenging. Here, we report that this can be solved by adding a cyclopropyl (CP) cap to the diene moiety of the original substrates. The resulting cyclopropyl-capped diene-ynes/diene-enes can react with CO under Rh catalysis to give [4+2+1] cycloadducts exclusively without forming [2+2+1] products. This reaction has a broad scope and can be used to synthesize useful 5/7 bicycles with CP moiety. Of the same importance, the CP moiety in the [4+2+1] cycloadducts can act as the intermediate group for further transformations so that other challenging bicyclic 5/7 and tricyclic 5/7/5 and 5/7/6, 5/7/7 skeletons, which are widely found in natural products, can be obtained. The mechanism of this [4+2+1] reaction has been investigated by quantum chemistry calculations, and the role of the CP group in avoiding the possible side reaction of [2+2+1] reaction have been identified, showing that the [4+2+1] is controlled by releasing the ring strain in the methlenecyclopropyl (MCP) group (about 7 kcal/mol) in the CP-capped dienes.

Keywords

[4+2+1]
[2+2+1]
cycloaddition
Rh
Mechanism
strain-release

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.