Allenes Chemistry And Stereochemistry – 1

The Molecule with no chiral center but chiral are called allenes, cumulenes with even no of double bonds.

Biphenyls and similar compounds in which chirality is due to the restricted rotation of single bonds.

Allenes, alkylidenes cycloalkanes, biphenyls, and so on are said to possess a chiral axis if we stretch a tetrahedron along its S₄ axis.

Synthesis of optically active allenes;

1. Kinetic resolution by incomplete reduction with tetra – α – pinanyl diborane. This method is simple but enantiomeric purity of the products is generally low.
2. Synthesized from precursours having chiral centers via reductive rearrangement.
3. synthesis of allenes from cyclo propane derivatives.
4. Also ortho claise rearrangement has been used.