通过对形阻断和转移进行生物活性环丁和二环丁异构体的立体选择性固态合成

In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...

Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers....

The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are stereoisomers that are not mirror images of each other. Substituted alkenes, such as the cis and trans isomers of 2-butene, are diastereomers, as these molecules exhibit different spatial orientations of their constituent atoms, are not mirror images of each other, and do not interconvert. Here, the interconversion is suppressed due to...