Thexyl borane hydroboration with

On the other hand, the observed syn preference of 59a is consistent with a study of hydroboration of 59a with diborane by Schueler and Rhodes [127], who obtained a mixture of the monoalcohols (symanti = 74 26) upon oxidative work-up. A similar magnitude of. yyn-preference was found (syn anti = 73 27) in the hydroboration with a bulkier borane, 2,3-dimethyl-2-butylborane (thexyl borane) [127]. This lack of effect of the bulk of the reagent in the hydroboration of 59a is consistent with the idea that the n face of 59a is free from steric bias [127], and that the syn preference of 59a found in dihydroxylation and epoxidation is non-sterically determined [128]. 

Hydroboration reaction of the terminal double bond of polystyrene with thexyl-borane yielded a polymer bearing one organoboron unit at the center of the polymer... 

These bulkier boranes enhance the regio selectivity of hydrobora tion of trisubstituted alkenes in particular and may also lead to high diastereoselectivity when there is a stereogenic centre next to the alkene. In this next examplej an allylic alcohol is hydroborated with thexyl borane. Oxidation reveals complete regioselectivity and a 9 1 stereoselectivity in favour of hydroboration on the same side as the OH group. 

Similarly, the hydroboration of 2,4,4-trimethyl-pentene with 1 equiv 2,3-dimethyl-2-butyl (thexyl) borane followed by heating the mixture at 200°C gives, after oxidation, 2,4,4-trimethyl-l,5-pentanediol in 81 % yield ... 

There are a wide variety of hydroborating reagents, including BH3 complexes, pinacolborane, thexyl borane, and catechol borane. The following employs 9-borabicyclo[3.3.1]nonane (9-BBN), which places the boron on the less sterically hindered carbon with high regioselectivity however, completely removing the cyclooctane by-products can be problematic. The alkylborane can be isolated, but is typically used directly in the next reaction, in this case oxidation to the primary alcohol. 

RCH=CH2- RCH2C00H. This conversion can be effected in >80% overall yield by hydroboration of 1-alkenes with HBBr2 S(CH3)3, H2BBr S(CH3)2, thexyl-borane (H2BThx), or dicyclohexylborane (HBChx2), followed by hydrolysis to form RCH2B(0H)2. The final step is oxidation of RCH2B(OH)2 to RCOOH, which can be... 

Hydroboration of 1-bromo-l-alkynes with chloro(thexyl)-borane leads to the synthesis of alkynyl ketones in 61-63% yields by the sequence of reactions shown in eq 5. Sequential treatment of alkenylchloro(thexyl)boranes, which are formed by the reaction of chloro(thexyl)borane with alkynes, with lithium chloro-propargylide and aldehydes affords 1,3-enynols or 1,2,4-trienols depending on the reaction conditions. ... 

Reductive Cyclization of (<>-Azidoalkenes. Hydroboration of < >-azidoalkenes with chloro(thexyl)borane followed by hydrolysis affords, via an intramolecular reductive cyclization, the corresponding p)UTolidine (78%) or the piperidine (53%) (eq 7). ... 

Hydroboration Polymerization of Diynes with Thexyl-borane... 

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