Nitroalkanes in C--C Bond Forming Reactions: a Crystal Structure of a Complex of a Guanidine Catalyst and a Nitroalkane Substrate.

Artificial Organic Host Molecules for Anions

“…The successful complexation of anions led to the idea that anionic transition states and reaction intermediates might also be stabilized by interactions with guanidinium compounds, thus making them act as catalysts. The isolation and X-ray structure of a complex between a bicyclic guanidine and R-nitrotoluene 311,312 confirmed an interaction pattern as sketched in Figure 9 and led to testing of the catalytic activity of a number of guanidines in nitroaldol reactions. Especially, it was hoped that the use of chiral guanidines would lead to enantiomerically enriched products.…”

“…A possible chirality transfer from the guanidinium host was not observed.

9 Sketch of the X-ray structure of the ion pair formed from the reaction of a bicyclic guanidine and α-nitrotoluene indicating the peculiar binding mode. ,

10 The concept of catalysis of Michael additions by 96

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“…Sketch of the X-ray structure of the ion pair formed from the reaction of a bicyclic guanidine and α-nitrotoluene indicating the peculiar binding mode. , …”

Kinetic and equilibrium study of the deprotonation of 4-nitrophenyl[bis(ethylsulphonyl)]methane by organic bases in acetonitrile in the presence of common cation BH+ and tetrabutylammonium perchlorate

“…Taking into account that both bases are of equal strength, the much faster reaction of TBD indicates that the Brønsted relationship does not hold. Such results could indicate the importance of steric factors, or as in this case, prove different reaction mechanism via two distinct structures of the transition state [4,30,31].…”