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Questions tagged [organoboron-compounds]

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4
votes
1answer
75 views

Stereoselectivity of Roush crotylboration

One can use a tartrate derived boronate to enact enantioselective crotyl transfer. Eg in scheme below: I do not understand how the stereoselectivity arises. We have a chiral boronate, true, and we ...
4
votes
0answers
72 views

Rationalise the Relative Reactivity of Borane and DIBAL as Reductants

In Clayden's Organic Chemistry (Second Edition) it is written that borane is useful in chemoselectively reducing the most nucleophilic carbonyl to its corresponding alcohol. It is later said that ...
10
votes
1answer
2k views

What happens when an alkylborane is treated with acetic acid?

In the hydroboration reactions of alkenes I've seen so far, they were always followed by oxidation with $\ce{H2O2/NaOH}$ (to yield alcohols). Today I found a peculiar reaction in which acetic acid-...
3
votes
1answer
152 views

Why is an alkoxide released instead of hydroxide in the attack of trialkyloxyborane by hydroxide?

In the mechanism of a hydroboration-oxidation, the oxidation part includes a nucleophilic attack of a hydroxide on a trialkyloxyborane ( $\ce{B(OR)_3}$ where $\ce{R}$ is an alkyl group). It creates ...
6
votes
1answer
610 views

Why does boron add to the less substituted carbon in the hydroboration of an alkene?

In the hydroboration of a typical alkene, the boron fragment ends up attached to the less substituted carbon: What are the electronic or steric factors that lead to this regioselectivity?
14
votes
1answer
1k views

Why is 1H-borepine aromatic?

For a compound to be aromatic, each atom in the ring must be a part of conjugation. Boron here has no lone pair, so how can 1⁠H-borepine be aromatic as I was told by someone?
2
votes
0answers
289 views

Selectivity in Suzuki coupling of 2,4-dichloropyrimidine

I've seen many papers (see e.g. Synthesis 2010, 16, 2721–2724) in which the 4-chloro group of 2,4-dichloropyrimidine is selectively reacted under Suzuki coupling conditions. Is there any way where ...
2
votes
1answer
361 views

What is the stereochemistry resulting from hydroboration of 1-methylcyclopentene?

What is the major product of the following reaction sequence? I'm supposed to work out the structures of both 2 and 3, but I already know 2 to be 1-methylcyclopentene (as the most substituted ...
7
votes
2answers
978 views

Hydroboration/oxidation vs acid-catalyzed hydration of 1-phenylpropene

I am trying to predict the products of both the hydroboration/oxidation and acid-catalyzed hydration of 1-phenylpropene: Both C1 and C2 of the double bond are secondary carbons. However, I have the ...