Double inversion, azoalkanes

W. Adam and A. V. Trofimov, Photomechanistic aspects of bicyclic azoalkanes triplet states, photoreduction, and double inversion. Chapter 93 in ref. 22. 

The first investigation on the stereoselectivity of the stepwise thermal denitrogena-tion of the diethoxy-substituted azoalkane has been reported. The double inversion product was the major isomer of the ring closure product. In photochemical denitro-genation, the inverted azoalkane was also the major isomer at 70 °C, although the stereoselectivity of the reaction was temperature dependent. An inversion process was proposed as the mechanism that determines the stereochemistry of the denitrogenation reaction products. The inversion product may alternatively be formed as a result of dynamic effects. 

Photomechanistic Aspects of Bicyclic Azoalkanes Triplet States, Photoreduction, and Double Inversion... 

This contribution is preceded by an earlier chapter, which covered the main topics of the photochemistry of cyclic azoalkanes for over three decades. Herein, we address the following mechanistic aspects of cyclic azoalkane photochemistry (1) the generation of azoalkane triplet states on direct irradiation and their photochemical transformations, and (2) the double inversion of the molecular skeleton in the formation of housane during photochemical nitrogen extrusion. 

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