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  2. Disiamylborane - Wikipedia

    en.wikipedia.org/wiki/Disiamylborane

    Disiamylborane is prepared by hydroboration of trimethylethylene with diborane. [1] The reaction stops at the secondary borane due to steric hindrance. Disiamylborane is relatively selective for terminal alkynes and alkenes vs internal alkynes and alkenes. Like most hydroboration, the addition proceeds in an anti-Markovnikov manner. [1]

  3. Hydroboration–oxidation reaction - Wikipedia

    en.wikipedia.org/wiki/Hydroboration–oxidation...

    Hydroboration–oxidation is an anti-Markovnikov reaction, with the hydroxyl group attaching to the less-substituted carbon. The reaction thus provides a more stereospecific and complementary regiochemical alternative to other hydration reactions such as acid-catalyzed addition and the oxymercuration–reduction process.

  4. Syn and anti addition - Wikipedia

    en.wikipedia.org/wiki/Syn_and_anti_addition

    In organic chemistry, syn-and anti-addition are different ways in which substituent molecules can be added to an alkene (R 2 C=CR 2) or alkyne (RC≡CR).The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.

  5. Hydroboration - Wikipedia

    en.wikipedia.org/wiki/Hydroboration

    In terms of regiochemistry, hydroboration is typically anti-Markovnikov, i.e. the hydrogen adds to the most substituted carbon of the double bond. That the regiochemistry is reverse of a typical HX addition reflects the polarity of the B δ+-H δ− bonds. Hydroboration proceeds via a four-membered transition state: the hydrogen and the boron ...

  6. Organoboron chemistry - Wikipedia

    en.wikipedia.org/wiki/Organoboron_chemistry

    Among hindered dialkylboranes is disiamylborane, abbreviated Sia 2 BH. It also is a dimer. Owing to its steric bulk, it selectively hydroborates less hindered, usually terminal alkenes in the presence of more substituted alkenes. [12] Disiamylborane must be freshly prepared as its solutions can only be stored at 0 °C for a few hours.

  7. Chiral auxiliary - Wikipedia

    en.wikipedia.org/wiki/Chiral_auxiliary

    In addition, transformations with chiral auxiliaries tend to be versatile and very well-studied, allowing the most time-efficient access to enantiomerically pure products. [ 2 ] Furthermore, [ 7 ] the products of auxiliary-directed reactions are diastereomers , which enables their facile separation by methods such as column chromatography or ...

  8. Diastereomer - Wikipedia

    en.wikipedia.org/wiki/Diastereomer

    When the single bond between the two centres is free to rotate, cis/trans descriptors become invalid. Two widely accepted prefixes used to distinguish diastereomers on sp³-hybridised bonds in an open-chain molecule are syn and anti. Masamune proposed the descriptors which work even if the groups are not attached to adjacent carbon atoms.

  9. Arene substitution pattern - Wikipedia

    en.wikipedia.org/wiki/Arene_substitution_pattern

    Several methods exist in order to separate these isomers: Column chromatography will often separate these isomers, as the ortho is more polar than the para in general. Fractional crystallisation can be used to obtain pure para product, relying on the principle that it is less soluble than the ortho and thus will crystallise first.