Thexyl borane

An MAI having a cyclodiborazane group was synthesized by the reaction of thexyl borane, adipoyldini-trile, and AIBN. It was block copolymerized with St [69]. 

DimethyI-butyI-(2)-boran (Thexyl-boran, S. 53) reduzicrt Carbonsauren zu Aldehyden (S. 144f.), ist ein zweizahniges Hydroborierungsmittel (s.S. 56) und kann durch N,N-Diathyl-anilin stabilisiert werden2. 

Carbonsauren werden in Iangsamer Reaktion durch einen OberschuB von 2,3-Dimethyl- butyl-(2)- boran(Thexyl-boran) (2,5 Mol pro Mol Carbonsaure) zu Aldehyden reduziert man gibt die Carbonsaure bei -20° zum Reduktionsmittel in THF und erhitzt 36 Stdn. unter RiickfluB ... 

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. 

The method of choice for the synthesis of borepins, benzoborepins, and heterole-fused borepins is reaction of the corresponding stannepins with boron trihalides or aryl dihaloboron compounds (see Section 14.20.10). A dibenzodi-hydroborepin has been prepared by a [6+l]-type cyclization of a naphthalene-1,8-diborane with BC13 (see Section 14.20.9.1). Yields of these methods are comparable. The saturated systems are typically prepared by reaction of 1,6-heptadienes with monoalkyl boranes such as thexyl borane (see Section 14.20.6.1). 

Preparation. The reagent is prepared by the reaction of (9 )-limonene with thexyl-borane (2, 148 this volume) to give the trialkylborane, This is converted into the borohydride ion (1) by treatment with t-butyllilhium in THF. 

HYDROBORATION Bis[3-methy 1-2-butyl] borane. 9-Borabicyclo[3.3.1 ]-nonane. Borane-l,4-oxathiane. Thexyl-borane. 

There are a wide variety of hydroborating reagents, including BH3 complexes, pinacolborane, thexyl borane, and catechol borane. The following employs... 

Not everyone wants to use carbon monoxide and a more convenient, though equally deadly, one-carbon reagent is cyanide ion. This does not require the high pressures often needed to make CO react.39 Cyanide forms stable ate complexes 247 with boranes and we shall use two different alkenes to illustrate this possibility. Thexyl borane 227 is essential for reaction with two different alkenes and it is better to use the more hindered alkene first. These precautions lead to a more selective reaction with the first alkene. 

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). ... 

Alkylchloro(thexyl)boranes prepared from terminal alkenes can be hydrolyzed with one equivalent of water and then oxidized with pyridinium chlorochromate (PCC) to the corresponding aldehyde in moderate yields (eq 6). ... 

Reduction of Carboxylic Acids to Aldehydes. Aliphatic carboxylic acids are reduced rapidly (15 min) and aromatic carboxylic acids are reduced slowly (24 h) by chloro(thexyl)borane-... 

---