Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides

Evan P. Beaumier; Meghan E. McGreal; Adam R. Pancoast; R. Hunter Wilson; James T. Moore; Brendan J. Graziano; Jason D. Goodpaster; Ian A. Tonks

doi:10.1021/acscatal.9b04107

Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides

Evan P. Beaumier, Meghan E. McGreal, Adam R. Pancoast, R. Hunter Wilson, James T. Moore, Brendan J. Graziano, Jason D. Goodpaster, Ian A. Tonks

Chemistry (Twin Cities)

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

29 Scopus citations

Abstract

Simple Ti imido halide complexes such as [Br₂Ti(N^tBu)py₂]₂ are competent catalysts for the synthesis of unsymmetrical carbodiimides via Ti-catalyzed nitrene transfer from diazenes or azides to isocyanides. Both alkyl and aryl isocyanides are compatible with the reaction conditions, although product inhibition with sterically unencumbered substrates sometimes limits the yield when diazenes are employed as the oxidant. The reaction mechanism has been investigated both experimentally and computationally, wherein a key feature is that the product release is triggered by electron transfer from an η²-carbodiimide to a Ti-bound azobenzene. This ligand-to-ligand redox buffering obviates the need for high-energy formally Ti^II intermediates and provides further evidence that substrate and product "redox noninnocence" can promote unusual Ti redox catalytic transformations.

Original language	English (US)
Pages (from-to)	11753-11762
Number of pages	10
Journal	ACS Catalysis
Volume	9
Issue number	12
DOIs	https://doi.org/10.1021/acscatal.9b04107
State	Published - Dec 6 2019

Bibliographical note

Funding Information:
Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231, for providing resources that contributed to the results reported within this paper.

Funding Information:
Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231 for providing resources that contributed to the results reported within this paper.

Publisher Copyright:
Copyright © 2019 American Chemical Society.

Keywords

carbodiimide
isocyanide
nitrene transfer
redox catalysis
redox non-innocence
titanium

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10.1021/acscatal.9b04107

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@article{bfcc1f265d294b6ab076c09e06e8a20a,

title = "Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides",

abstract = "Simple Ti imido halide complexes such as [Br2Ti(NtBu)py2]2 are competent catalysts for the synthesis of unsymmetrical carbodiimides via Ti-catalyzed nitrene transfer from diazenes or azides to isocyanides. Both alkyl and aryl isocyanides are compatible with the reaction conditions, although product inhibition with sterically unencumbered substrates sometimes limits the yield when diazenes are employed as the oxidant. The reaction mechanism has been investigated both experimentally and computationally, wherein a key feature is that the product release is triggered by electron transfer from an η2-carbodiimide to a Ti-bound azobenzene. This ligand-to-ligand redox buffering obviates the need for high-energy formally TiII intermediates and provides further evidence that substrate and product {"}redox noninnocence{"} can promote unusual Ti redox catalytic transformations.",

keywords = "carbodiimide, isocyanide, nitrene transfer, redox catalysis, redox non-innocence, titanium",

author = "Beaumier, {Evan P.} and McGreal, {Meghan E.} and Pancoast, {Adam R.} and Wilson, {R. Hunter} and Moore, {James T.} and Graziano, {Brendan J.} and Goodpaster, {Jason D.} and Tonks, {Ian A.}",

note = "Funding Information: Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231, for providing resources that contributed to the results reported within this paper. Funding Information: Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231 for providing resources that contributed to the results reported within this paper. Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",

year = "2019",

month = dec,

day = "6",

doi = "10.1021/acscatal.9b04107",

language = "English (US)",

volume = "9",

pages = "11753--11762",

journal = "ACS Catalysis",

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T1 - Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides

AU - Beaumier, Evan P.

AU - McGreal, Meghan E.

AU - Pancoast, Adam R.

AU - Wilson, R. Hunter

AU - Moore, James T.

AU - Graziano, Brendan J.

AU - Goodpaster, Jason D.

AU - Tonks, Ian A.

N1 - Funding Information: Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231, for providing resources that contributed to the results reported within this paper. Funding Information: Financial support was provided by the National Institutes of Health (1R35GM119457), and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Instrumentation for the University of Minnesota Chemistry NMR facility was supported from a grant through the National Institutes of Health (S10OD011952). X-ray diffraction experiments were performed with a diffractometer purchased through a grant from NSF/MRI (1229400) and the University of Minnesota. We acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231 for providing resources that contributed to the results reported within this paper. Publisher Copyright: Copyright © 2019 American Chemical Society.

PY - 2019/12/6

Y1 - 2019/12/6

N2 - Simple Ti imido halide complexes such as [Br2Ti(NtBu)py2]2 are competent catalysts for the synthesis of unsymmetrical carbodiimides via Ti-catalyzed nitrene transfer from diazenes or azides to isocyanides. Both alkyl and aryl isocyanides are compatible with the reaction conditions, although product inhibition with sterically unencumbered substrates sometimes limits the yield when diazenes are employed as the oxidant. The reaction mechanism has been investigated both experimentally and computationally, wherein a key feature is that the product release is triggered by electron transfer from an η2-carbodiimide to a Ti-bound azobenzene. This ligand-to-ligand redox buffering obviates the need for high-energy formally TiII intermediates and provides further evidence that substrate and product "redox noninnocence" can promote unusual Ti redox catalytic transformations.

AB - Simple Ti imido halide complexes such as [Br2Ti(NtBu)py2]2 are competent catalysts for the synthesis of unsymmetrical carbodiimides via Ti-catalyzed nitrene transfer from diazenes or azides to isocyanides. Both alkyl and aryl isocyanides are compatible with the reaction conditions, although product inhibition with sterically unencumbered substrates sometimes limits the yield when diazenes are employed as the oxidant. The reaction mechanism has been investigated both experimentally and computationally, wherein a key feature is that the product release is triggered by electron transfer from an η2-carbodiimide to a Ti-bound azobenzene. This ligand-to-ligand redox buffering obviates the need for high-energy formally TiII intermediates and provides further evidence that substrate and product "redox noninnocence" can promote unusual Ti redox catalytic transformations.

KW - carbodiimide

KW - isocyanide

KW - nitrene transfer

KW - redox catalysis

KW - redox non-innocence

KW - titanium

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DO - 10.1021/acscatal.9b04107

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JF - ACS Catalysis

IS - 12

ER -

Carbodiimide Synthesis via Ti-Catalyzed Nitrene Transfer from Diazenes to Isocyanides

Abstract

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