Unsymmetrical 1,1-bis(boryl)alkanes and alkenes are organo-bismetallic equivalents, which are synthetically important because they allow for sequential selective transformations of C–B bonds. We reviewed the synthesis and chemical reactivity of 1,1-bis(boryl)alkanes and alkenes to provide information for the synthetic community. In the first part of this review, we disclose the synthesis and chemical reactivity of unsymmetrical 1,1-bisborylalkanes. In the second part, we describe the synthesis and chemical reactivity of unsymmetrical 1,1-bis(boryl)alkenes.
Although
gem
-diborylalkenes are known to be among
the most valuable reagents in modern organic synthesis, providing
a rapid access to a wide array of transformations, including the construction
of C–C and C-heteroatom bonds, their use as dienophile-reactive
groups has been rare. Herein we report the Diels–Alder (DA)
reaction of (unsymmetrical)
gem
-diborylalkenes. These
reactions provide a general and efficient method for the stereoselective
conversion of
gem
-diborylalkenes to rapidly access
1,1-bisborylcyclohexenes. Using the same DA reaction manifold with
borylated-dienes and
gem-
diborylalkenes, we also
developed a concise, highly regioselective synthesis of 1,1,2-tris-
and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds
that currently lack efficient synthetic access. Furthermore, DFT calculations
provided insight into the underlying factors that control the chemo-,
regio-, and stereoselectivity of these DA reactions. This method also
provides stereodivergent syntheses of
gem-
diborylnorbornenes.
The utility of the
gem-
diborylnorbornene building
blocks was demonstrated by ring-opening metathesis polymerization
(ROMP), providing a highly modular approach to the first synthesis
of the
gem-
diboron-based polymers. Additionally,
these polymers have been successfully submitted to postpolymerization
modification reactions. Given its simplicity and versatility, we believe
that this novel DA and ROMP approach holds great promise for organoboron
synthesis as well as organoboron-based polymers and that it will result
in more novel transformations in both academic and industrial research.
Although gem-diborylalkenes are known to be among the most valuable reagents in modern organic synthesis, providing a rapid access to a wide array of transformations, including the construction of C−C and C‐heteroatom bonds, their use as dienophile-reactive groups has been rare. Herein we report the Diels-Alder (DA) reaction of (unsymmetrical) gem-diborylalkenes. These reactions provide a general and efficient method for the stereoselective conversion of gem-diborylalkenes to rapidly access 1,1-bisborylcyclohexenes. Using the same DA reaction manifold with borylated-dienes and gem-diborylalkenes, we also developed a concise, highly regioselective synthesis of 1,1,2-tris- and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds that currently lack efficient synthetic access. Furthermore, DFT calculations provided insight into the underlying factors that control the chemo-, regio, and stereoselectivity of these DA reactions. This method also provides stereodivergent syntheses of gem-diboryl-norbornenes. The utility of the gem-diboryl-norbornene building blocks was demonstrated by ring-opening metathesis polymerization (ROMP), providing a highly modular approach to the first synthesis of the gem-diboron-based polymers. Given its simplicity and versatility, we believe that this novel DA and ROMP approach holds great promise for organoboron synthesis as well as organoboron-based polymers and that it will result in more novel transformations in both academic and industrial research.<br>
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