Microwave assisted organic synthesis-a review

Recent Advances in the Baylis−Hillman Reaction and Applications

2. Essential Components: Earlier Developments 5449 2.1. Activated alkenes/alkynes 5450 2.1.1. Acyclic activated alkenes/ alkynes 5450 2.1.2. Cyclic activated alkenes 5451 2.2. Electrophiles 5451 2.3. Catalysts 5452 3. Essential Components: Recent Developments 5452 3.1. Activated Alkenes/Alkynes 5452 3.2. Electrophiles 5460 3.3. Catalysts 5477 4. Asymmetric Baylis-Hillman Reaction: Earlier Developments 5495

Recent contributions from the Baylis-Hillman reaction to organic chemistry.

Insofar as one of the fundamental objectives of organic synthesis is the construction of complex molecules from simpler ones, the importance of synthetic efficiency becomes immediately apparent and has been well-recognized.1 The increase in molecular complexity2 that necessarily accompanies the course of a synthesis provides a guide (and a measure) of synthetic efficiency. As a goal, one would like to optimally match the change in molecular complexity at each step with reactions of comparable synthetic complexity. Thus, the creation of many bonds, rings, and stereocenters in a single transformation is a necessary (though not sufficient) condition for high synthetic efficiency. The ultimate, perfect match would constitute single-step syntheses. More realistically, especially in view of the desire for general synthetic methods, the combination of mulScott E. Denmark was born in New York in 1953. He obtained an S.B. degree from MIT in 1975 and carried out research with Daniel Kemp and Richard Holm. His graduate studies at the ETH-Zurich with Albert Eschenmoser culminated with the D. Sc. Tech. degree in 1980. That same year he joined the faculty of the University of Illinois at UrbanasChampaign and was promoted to full professor in 1987. In 1991 he was named the Reynold C. Fuson Professor of Chemistry. His research interests are primarily in the invention of new synthetic reactions, structure and reactivity of organoelement reagents, and the origin of stereocontrol in fundamental carbon−carbon bond forming reactions.

Tandem [4+2]/[3+2] Cycloadditions of Nitroalkenes.

Asymmetric 1,3-dipolar cycloadditions

Thiones as Superdipolarophiles. Rates and Equilibria of Nitrone Cycloadditions to Thioketones

Cycloaddition entre l'acrylonitrile ou l'acrylate de methyle et des benzylidene alkyl ammonioolates pour conduire a des isoxazolidines substituees. Orientation

Regioselectivity associated with the 1,3-dipolar cycloaddition of nitrones with electron-deficient dipolarophiles

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

Rate measurements reveal the superiority of C = S bonds over CC multiple bonds as dipolarophiles in cycloadditions of thiobenzophenone S-me- thylide, diphenyldiazomethane, and N-methyl-C-phenylnitrone. Thione S-oxi- des (sulfines) and thione S-sulfides likewise prefer thiones as cycloaddition partners. Many cycloadditions of thiones .approach equilibria; the high reacti- vity is a kinetic phenomenon, the low HO-LU distance of the a-MOs being re- sponsible. Ab initio calculations for %C=S + %C=NH+-O- result in a ne- gative activation energy. a Bonds with silicon, phosphorus etc. exhibit likewise low HO-LU gaps and increased reactivity.

Lubor Fišera

Papers

Thiones as Superdipolarophiles. Rates and Equilibria of Nitrone Cycloadditions to Thioketones

Regioselectivity associated with the 1,3-dipolar cycloaddition of nitrones with electron-deficient dipolarophiles

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

New thione chemistry

Reversal of Diastereoselectivity of Nitrile Oxide 1,3-Dipolar Cycloadditions by Mg(II). Acceleration of Cycloaddition by Microwave Irradiation