Magnesium-Mediated Nucleophilic Borylation of Carbonyl Electrophiles

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Abstract

The diboranate derivative, [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}], resulting from treatment of a β-diketiminato magnesium n-butyl derivative with the commercially available diborane, B2pin2, reacts as a source of the [Bpin] nucleophile with ketones and organic isocyanates. Reactions with benzophenone and 9-fluorenone afford products, which may be rationalized as enolate species resulting from kinetically controlled dearomatization rather than the thermodynamically preferred C-borylation of the electrophilic C═O unit provided by a previously described magnesium complex bearing a terminal [Bpin] nucleophile. The enolate derivatives react readily with further equivalents of the ketones to provide C–C coupling and tetra-alkoxyborate products via aldol condensation processes. In contrast to this divergent behavior, isocyanates with [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}] react like the terminal boryl species to yield the anticipated C-boryl amidate products. Although we have yet to identify the origin of this contrasting reactivity, these results indicate the potential of these systems, which are ostensibly both sources of identical [Bpin] nucleophiles, to provide divergent and highly selective access to kinetic or thermodynamic reaction products.
LanguageEnglish
Number of pages8
JournalOrganometallics
Early online date31 Aug 2018
DOIs
StatusPublished - 31 Aug 2018

Cite this

@article{c52379979b73434f90020a67bf840e0f,
title = "Magnesium-Mediated Nucleophilic Borylation of Carbonyl Electrophiles",
abstract = "The diboranate derivative, [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}], resulting from treatment of a β-diketiminato magnesium n-butyl derivative with the commercially available diborane, B2pin2, reacts as a source of the [Bpin] nucleophile with ketones and organic isocyanates. Reactions with benzophenone and 9-fluorenone afford products, which may be rationalized as enolate species resulting from kinetically controlled dearomatization rather than the thermodynamically preferred C-borylation of the electrophilic C═O unit provided by a previously described magnesium complex bearing a terminal [Bpin] nucleophile. The enolate derivatives react readily with further equivalents of the ketones to provide C–C coupling and tetra-alkoxyborate products via aldol condensation processes. In contrast to this divergent behavior, isocyanates with [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}] react like the terminal boryl species to yield the anticipated C-boryl amidate products. Although we have yet to identify the origin of this contrasting reactivity, these results indicate the potential of these systems, which are ostensibly both sources of identical [Bpin] nucleophiles, to provide divergent and highly selective access to kinetic or thermodynamic reaction products.",
author = "Michael Hill and Mary Mahon and Anne-Frederique Pecharman and Claire McMullin",
year = "2018",
month = "8",
day = "31",
doi = "10.1021/acs.organomet.8b00408",
language = "English",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",

}

TY - JOUR

T1 - Magnesium-Mediated Nucleophilic Borylation of Carbonyl Electrophiles

AU - Hill, Michael

AU - Mahon, Mary

AU - Pecharman, Anne-Frederique

AU - McMullin, Claire

PY - 2018/8/31

Y1 - 2018/8/31

N2 - The diboranate derivative, [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}], resulting from treatment of a β-diketiminato magnesium n-butyl derivative with the commercially available diborane, B2pin2, reacts as a source of the [Bpin] nucleophile with ketones and organic isocyanates. Reactions with benzophenone and 9-fluorenone afford products, which may be rationalized as enolate species resulting from kinetically controlled dearomatization rather than the thermodynamically preferred C-borylation of the electrophilic C═O unit provided by a previously described magnesium complex bearing a terminal [Bpin] nucleophile. The enolate derivatives react readily with further equivalents of the ketones to provide C–C coupling and tetra-alkoxyborate products via aldol condensation processes. In contrast to this divergent behavior, isocyanates with [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}] react like the terminal boryl species to yield the anticipated C-boryl amidate products. Although we have yet to identify the origin of this contrasting reactivity, these results indicate the potential of these systems, which are ostensibly both sources of identical [Bpin] nucleophiles, to provide divergent and highly selective access to kinetic or thermodynamic reaction products.

AB - The diboranate derivative, [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}], resulting from treatment of a β-diketiminato magnesium n-butyl derivative with the commercially available diborane, B2pin2, reacts as a source of the [Bpin] nucleophile with ketones and organic isocyanates. Reactions with benzophenone and 9-fluorenone afford products, which may be rationalized as enolate species resulting from kinetically controlled dearomatization rather than the thermodynamically preferred C-borylation of the electrophilic C═O unit provided by a previously described magnesium complex bearing a terminal [Bpin] nucleophile. The enolate derivatives react readily with further equivalents of the ketones to provide C–C coupling and tetra-alkoxyborate products via aldol condensation processes. In contrast to this divergent behavior, isocyanates with [HC{(Me)CNDipp}2Mg{pinBB(n-Bu)pin}] react like the terminal boryl species to yield the anticipated C-boryl amidate products. Although we have yet to identify the origin of this contrasting reactivity, these results indicate the potential of these systems, which are ostensibly both sources of identical [Bpin] nucleophiles, to provide divergent and highly selective access to kinetic or thermodynamic reaction products.

U2 - 10.1021/acs.organomet.8b00408

DO - 10.1021/acs.organomet.8b00408

M3 - Article

JO - Organometallics

T2 - Organometallics

JF - Organometallics

SN - 0276-7333

ER -