IntermolecularCyclization Reactions to form Carbocycles

Abstract

General Introduction [2 + 2] Cycloaddition Reactions D iels– A lder Reactions [6 + 4] Cycloaddition Reactions [8 + 2] Cycloaddition Reactions [2 + 2 + 2] Cycloaddition Reactions

Extraordinary Mechanism of the Diels–Alder Reaction: Investigation of Stereochemistry, Charge Transfer, Charge Polarization, and Biradicaloid Formation

“…The s -distance between the peaks will be a quantitative measure for the asynchronicity of bond formation. (v) Rate enhancement of the DA reaction is achieved by increasing the charge transfer from diene to dienophile, which is accomplished by electron-donating groups for the former and electron-withdrawing groups for the latter. − Catalysis of the DA reaction is possible by increasing the effect of the withdrawing groups, which can be achieved by suitable Lewis acids such as BF 3 . ,− (vi) The parent DA reaction has in water a higher barrier (0.71 kcal/mol, PCM calculations). Charge transfer and charge polarization in the parent DA reaction is too small to establish H-bonding between water and the dienophile.…”

“…The Diels–Alder (DA) reaction is one of the most applied and best investigated synthetic methods in chemistry − because of its relatively low reaction barrier, − the versatility of the parent noncatalyzed version, its acceleration by Lewis-acid catalysts, ,− or the possibilities provided by the retro-DA, − and the hetero-DA reaction. , In the DA reaction, a diene such as 1,3-butadiene (BD) undergoes a cycloaddition with a dienophile such as ethene (E), which implies that three π-bonds are broken and two new σ- and one new π-bond are formed. Apart from these chemical processes, there are important pre- and postchemical processes that have to take place in the reaction complex (RC) to make the cycloaddition possible.…”

A Simple Method for Resolution ofEndo‐/Exo‐Monoesters ofTrans‐Norborn‐5‐Ene‐2,3‐Dicarboxylic Acids Into Their Enantiomers

“…They were used in the syntheses of a great number of organic compounds of various classes . To build up norbornene structures, the Diels‐Alder reaction is frequently used . However, the number examples of successful introduction of derivatized fumaric and maleic acids in this reaction known so far is limited and, as a rule, it requires the use of chiral modifiers or catalysts …”