On the Thermodynamic Control of Ring Opening of 4-Substituted 1,3,3-Tris-Carbethoxycyclobutene and the Role of the C-3 Substituent in Masking the Kinetic Torquoselectivity

06 August 2020, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The predominant transformations of 4-methyl- and 4-phenyl-1,3,3-tris-carbethoxycyclobutenes to s-trans-trans-1,1,3-tris-carbethoxy-4-methyl- and 4-phenyl-1,3-butadienes, respectively, proceed through a pathway entailing heterolytic cleavage of sC3C4 bond rather than the usual four-electron conrotatory ring opening. The adventitious or in situ generated halogen acid catalyzes the reaction by either protonation of one of the two ester groups on C3 and, thus, weakening sC3C4 bond to allow its heterolytic cleavage and formation of a stable cation or protonation followed by halide ion attack in SN2 manner on the methyl/phenyl-bearing carbon. Reorganization of the cation species formed in the former event and elimination of the elements of halogen acid from the halo-species formed in the latter event generate the observed product. The nucleophilic attack of DMSO to bring about heterolytic SN2 cleavage of sC3C4 bond is also discussed.

Keywords

1,3,3-tris-carbethoxy-4-methylcyclobutene
1,3,3-tris-carbethoxy-4-phenylcyclobutene
torquoselectivity
DFT quantum chemical transition state calculation
heterolytic cleavage

Supplementary materials

Title
Description
Actions
Title
Supplementary Information
Description
Actions
Title
manuscript 05082020
Description
Actions
Title
Supporting Information 05082020
Description
Actions

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.