Synthesis of Chromen[4,3-b]pyrrolidines by Intramolecular 1,3-Dipolar Cycloadditions of Azomethine Ylides: An Experimental and Computational Assessment of the Origin of Stereocontrol

Azomethine ylides, generated from imine-derived O-cinnamyl or O-crotonyl salicylaldeyde and α-amino acids, undergo intramolecular 1,3-dipolar cycloaddition, leading to chromene[4,3-b]pyrrolidines. Two reaction conditions are used: (a) microwave-assisted heating (200 W, 185 °C) of a neat mixture of reagents, and (b) conventional heating (170 °C) in PEG-400 as solvent. In both cases, a mixture of two epimers at the α-position of the nitrogen atom in the pyrrolidine nucleus was formed through the less energetic endo-approach (B/C ring fusion). In many cases, the formation of the stereoisomer bearing a trans-arrangement into the B/C ring fusion was observed in high proportions. Comprehensive computational and kinetic simulation studies are detailed. An analysis of the stability of transient 1,3-dipoles, followed by an assessment of the intramolecular pathways and kinetics are also reported.

Bundeswehr 3.0: The political, military and social dimensions of the reform of the German armed forces. OSW Point of View Number 28, May 2012

This reform of the Bundeswehr, launched in 2011, is the latest of the three decisive stages in the post-war transformation of the German armed forces. The reform aims at “constructing” the armed forces anew in the political, military and social dimensions.The present paper presents the evolution of the role of the armed forces in German foreign and security policy and the ongoing process of “constructing” a new Bundeswehr. It analyses the process of redefining the objectives and principles of: the Bundeswehr’s participation in international operations, its current military transformation, and changes in its image and social identity. It also presents the implications of this broader transformation for political and military.