Hydroboration of alkynes and alkenes

The addition of dialkyboranes such as 9-borabicyclo[3.3.1]nonane (9-BBN), disiamylborane, or dicyclohexylborane to i-alkenes gives alkylboron compounds [12]. The 

2 Cross-coupling of Organoboron Compounds with Organic Halides 

Terminal and internal (Z)-l-alkenylboronates are prepared from (Z)-(haloalkenyl)boronic esters (4) which can be readily obtained by hydroboration of 1-halo-1-alkynes [15, 17, 18]. 

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Scheme 4.S8. Zirconium- and rhodium-catalyzed hydroborations of alkenes and alkynes with pinacolborane.

We note that there are NMR-based kinetic studies on zirconocene-catalyzed pro-pene polymerization [32], Rh-catalyzed asymmetric hydrogenation of olefins [33], titanocene-catalyzed hydroboration of alkenes and alkynes [34], Pd-catalyzed olefin polymerizations [35], ethylene and CO copolymerization [36] and phosphine dissociation from a Ru-carbene metathesis catalyst [37], just to mention a few. 

Alkylboranes formed in the hydroboration of alkenes and alkynes seldom are isolated for the most part they are used as reactive intermediates for the synthesis of other substances. In the reactions of alkylboranes, the B-C bond... 

Hydroboration. The organoborane effects selective hydroboration of alkene and alkyne linkages in the presence of carbonyl group. ... 

Hydroboration of alkenes and alkynes is one of the most valuable synthetic techniques in organic chemistry because the organoboranes formed are readily converted into various kinds of organic compounds, and the enantioselective version developed by Brown has greatly expanded the scope of the hydroboration... 

Table 5. Synthesis of Alkyl- and Alkenylboron Derivatives by Hydroboration of Alkenes and Alkynes with Halogenoboranes...

Hydroboration. Brown and Gupta have reported results of an extensive study of the hydroboration of alkenes and alkynes (equations I and II). The... 

The attractiveness of organo-9-BBN derivatives as coupling partners is largely due to their accessibility via the hydroboration of alkenes and alkynes on the other hand, they suffer from the drawbacks of not being easily manipulated in air or commercially available. In contrast, boronic acids are air-stable, and a large number and variety are commercially available. Consequently, the development of methods for cross-coupling alkyl electrophiles with boronic acids is undoubtedly an important objective. 

Hydroboration. The complete paper on hydroboration of alkenes and alkynes with this resigent is available. ... 

Hydroboration of alkenes and alkynes is an established preparative method of alkyl- and alkenylboranes. Arylboranes, arylboronic acids and their esters (boronates) are prepared from aryllithium or Grignard reagents. 

The mechanisms of these reactions are varied, but can still be categorized. The hydrocyanations, hydrosilylations, and many of the hydroborations, occur with late-metal catalysts. These reactions occur by oxidative addition of the H-X bond, followed by migratory insertion of the olefin into the M-H or M-X bond, and reductive elimination to form the final product. Hydrocyanation occurs by insertion of the unsaturated reagent into the M-H bond, while hydrosilylation and hydroboration have been shown to occur by insertion of the olefin into the M-H bond in some cases and into the M-X bond in others. HydrosUy-lations and hydroborations of alkenes and alkynes catalyzed by (P transition metal complexes and by lanthanides follow a different pathway because these complexes caimot undergo oxidative addition. The mechanism of the reactions catalyzed by these complexes involves u-bond metatheses. 

Hydroboration of Alkenes and Alkynes. The hydroboration of alkenes with dichloroborane-dimethyl sulfide (DCBS) in refluxing dichloromethane produces considerable quantities of R2BCI and R3B as impurities, presumably as the result of disproportionation of the reagent. The addition of boron trichloride liberates dichloroborane and the hydroboration proceeds cleanly at25°C (eq 1). ... 

The hydroboration of alkenes and alkynes to highly chemo-, regio-, and stereoselective alkyl and vinyl boronic esters with pinacolborane is catalysed by bis(imino)pyridine Fe(II) complex with activating agent tolylMgBr in THF. Preliminary mechanistic experiments suggest that an Fe(I) catalyst may be formed under the reaction conditions. ... 

Hydroborations. Ph3SiH can convert tri- and dihaloboranes to the corresponding di- and monohaloboranes, which can then be used in the in situ hydroboration of alkenes and alkynes. Notably,... 

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