Cycloaddition reaction between azomethine ylides and p-deficient alkenes leads to densely substituted L-and D-unnatural prolines. These (3 + 2) cycloadducts in turn catalyse the preparation of an offspring of unnatural endo-and exo-L-proline derivatives. These latter compounds are also efficient catalysts of aldol reactions and yield aldol adducts with the opposite stereochemistry obtained under natural L-Pro organocatalysis.

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A silyne seeker: The synthesis of the first isolable silyne, which is stabilized by a phosphine ligand, has been achieved (see picture). An X‐ray diffraction study reveals a very short silicon–carbon bond, as predicted computationally for SiC bonds. This species has a certain degree of carbenic character, and this result shows that the phosphonium sila‐ylide fragment acts as a strong π‐donating and π‐accepting substituent.