[2 + 2]-Cycloadditions to Strained Bridgehead Olefins. II. Diphenylketene

The strained bridgehead olefins bicyclo [3.3.1]non-1-ene ( 1 ), bicyclo [4.2.1 ]non-1(8)-ene ( 2 ), and bicyclo [4.2.1]non-1-ene (3), and the comparable monocyclic (E)-1-methylcyclooctene ( 4 ) react with diphenylketene ( 6 ) to give a single cycloadduct 7 , 8 , 9 and 10 , respectively, in which the diphenyl-substituted C-atom is bound to the bridgehead. The structure of the cyclobutanone 8 has been determined by X-ray analysis of a twin crystal obtained by crystallization with spontaneous enrichment of enantiomers.     

[2 + 3]-Cycloadditions to C60 fullerene. Synthesis of pyrrolidinofullerenes

Pyrrolidinofullerenes were synthesized by reaction of C₆₀ fullerene with N-methylglycine and substituted aromatic aldehydes.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1695–1697.Original Russian Text Copyright © 2004 by Loginova, Gunkin.This revised version was published online in April 2005 with a corrected cover date.     

Photosensitized [4+2]- and [2+2]-Cycloaddition Reactions of N-Sulfonylimines

The synthesis of polycyclic compounds is of high interest due to the prevalence of these motifs in drugs and natural products. Herein, we report on the stereoselective construction of 3D bicyclic scaffolds and azetidine derivatives by modulation of N-sulfonylimines to achieve either [4+2]- or [2+2]-cycloaddition reactions. The utility of the method was established by further modulation of the product. Mechanistic studies are also included, which support reaction via Dexter energy transfer.     

Intermolecular [4 + 2]-Cycloadditions of Nitroalkenes with Cyclic Olefins. Transformations of Cyclic Nitronates

Nitrocyclohexene undergoes facile SnCl₄-induced, [4 + 2]-cycloadditions with simple cycloalkenes to produce nitronates. The nitronates can be transformed sterospecifically into a number of other functional groups (alcohol, ketone, oxime, amine) by hydrolytic, reductive, and oxidative processes. The mechanism of the [4 + 2]-cycloaddition is believed to involve formation of a zwitterionic intermediate which can collapse via competing pathways to form the observed products. 1,3-Dipolar cycloadditions of the nitronates are described.