5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents: characterization of derived 1,2-oxaborole radicals and boralactones

Wen Dai; Timothy R. McFadden; Dennis P. Curran; Herbert A. Früchtl; John C. Walton

doi:10.1021/jacs.8b09288

5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents: characterization of derived 1,2-oxaborole radicals and boralactones

Wen Dai, Timothy R. McFadden, Dennis P. Curran^*, Herbert A. Früchtl, John C. Walton^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5-endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH₃) and dimethyl acetylenedicarboxylate.

Original language	English
Pages (from-to)	15868-15875
Number of pages	8
Journal	Journal of the American Chemical Society
Volume	140
Issue number	46
Early online date	29 Oct 2018
DOIs	https://doi.org/10.1021/jacs.8b09288
Publication status	Published - 21 Nov 2018

Access to Document

10.1021/jacs.8b09288

Dai_2018_JACS_5-endocyclizations_AAM
Copyright © 2018 American Chemical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/jacs.8b09288
Accepted author manuscript, 788 KB

John Christopher Walton
- jcwst-andrews.acuk
- School of Chemistry - Emeritus Professor
- EaSTCHEM
Person: Emeritus Professor

Cite this

@article{8a558f4ea4ed4b04b58828a94bcd1b38,

title = "5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents: characterization of derived 1,2-oxaborole radicals and boralactones",

abstract = "EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5-endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.",

author = "Wen Dai and McFadden, {Timothy R.} and Curran, {Dennis P.} and Fr{\"u}chtl, {Herbert A.} and Walton, {John C.}",

note = "J.C.W. thanks EaStCHEM for financial support, and D.P.C. thanks the U.S. National Science Foundation. Computational support was provided through the EaStCHEM Research Computing Facility.",

year = "2018",

month = nov,

day = "21",

doi = "10.1021/jacs.8b09288",

language = "English",

volume = "140",

pages = "15868--15875",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society (ACS)",

number = "46",

}

TY - JOUR

T1 - 5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents

T2 - characterization of derived 1,2-oxaborole radicals and boralactones

AU - Dai, Wen

AU - McFadden, Timothy R.

AU - Curran, Dennis P.

AU - Früchtl, Herbert A.

AU - Walton, John C.

N1 - J.C.W. thanks EaStCHEM for financial support, and D.P.C. thanks the U.S. National Science Foundation. Computational support was provided through the EaStCHEM Research Computing Facility.

PY - 2018/11/21

Y1 - 2018/11/21

N2 - EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5-endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.

AB - EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5-endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.

U2 - 10.1021/jacs.8b09288

DO - 10.1021/jacs.8b09288

M3 - Article

C2 - 30369236

AN - SCOPUS:85056802947

SN - 0002-7863

VL - 140

SP - 15868

EP - 15875

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 46

ER -

5-endo cyclizations of NHC-boraallyl radicals bearing ester substituents: characterization of derived 1,2-oxaborole radicals and boralactones

Abstract

Access to Document

Fingerprint

Profiles

John Christopher Walton

Cite this