A-vinylboronates

A series of remarkable stoichiometric CH functionalization reactions have been employed, including transmetalla-tion with a vinylboronic acid moiety, to synthesize the core of teleocidin B-4 (Equation (200)).1... 

Radioiodination of vinylboronic acid derivatives has been applied443-445 for the synthesis of 17 tf-iodovinylestradiol derivatives443 (equations 206) and (E)-1 -[123I]iododecene, 306 (equation 207). In the iodination of a vinylboronic acid, chloramine-T has been found to be the most efficient oxidant under both carrier-added and NCA conditions and has been applied in reaction 207. 

Boron Reagents. Tetrazole can be lithiated in the 5-position and brominated to yield a 5-bromo substrate that reacts with a vinylboronic acid to furnish the corresponding vinyltetrazole 133 (Scheme 56). ... 

Regiocontrolled net hydroboration of terminal alkynes can also be realized due to the nature of NHC-Cu complex employed. Thus, with an iV-arylated NHC (e.g., IMes or IPr), a-vinylboronates are formed, while with a bulky 7V-alkyI NHC-Cu, the p-isomer prevails. Substrates such as propargyl ethers, amines, and a variety of aryl-substituted alkynes have all been studied. ... 

Need to use a vinylboronate as the starting material for the synthesis of a vinyl ether... 

This reaction has been developed and uses a common iridium catalyst for the conversion [102], This process is also attractive as it could be used to generate ethenyl ethers This is a challenging reaction and has been accomplished through copper-catalyzed cross-coupling chemistry using a trivinylcyclotriboroxane as a vinylboronic acid equivalent [108]. It has also been achieved using iridium catalysis [102]... 

SCHEME 3.118 Coupling of a vinylboronic acid with benzimidazole [125]. 

SCHEME 3.143 Nitration of a vinylboronic acid using bismuth nitrate [118]. 

SCHEME 6.39 Addition of B-Br bonds to alkynes and conversion into a vinylboronate [81]. 

A vinylboronate was prepared through a metal-free borylation reaction starting from a trisubstituted vinyl bromide (Scheme 6.41) [3]. The key in this chemistry was the use of... 

Need a transition metal-free synthesis of a vinylboronate... 

While ethenylboronic acid has been reported to be unstable, its cyclodehydration product (a cyclotriboroxane) was quite stable as its pyridine adduct. It successfully served as a vinylboronic acid equivalent in coupling reactions [96]... 

The direct addition of HF using DMPU/HF would be a good place to start [63]. Additionally, it might be more practical to convert the alkyne into a vinylboronate speeies and then to the vinyl fluoride [92]... 

Treatment of the alkyne with elemental iodine and a secondary phosphine oxide is a particularly attractive approach to the synthesis of vinyl iodides with Markovnikov selectivity [181]. An attractive entry point for this chemistry would he to convert the alkyne into a vinylboronate followed by the addition of iodine under basic conditions to afford the vinyl iodide [177]... 

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