The intermolecular cyclotrimerisation of terminal and internal alkynes can be catalysed by simple cobalt complexes such as a CoBr2(diimine) under mild reaction conditions when treated with zinc and zinc iodide with high regioselectivity in excellent yields.

[reaction: see text] Addition of trimethylsilyl cyanide to ketimines derived from (R)-2,2-dimethyl-1,3-dioxolan-4-yl methyl ketone to generate a quaternary stereocenter has been achieved with high yields and excellent diastereoselectivity. The stereoselectivity was found to be temperature and solvent dependent. The beta-hydroxy-alpha-amino nitrile of syn configuration was the major compound in kinetically controlled reactions, whereas the anti stereoisomer was obtained in excess in thermodynamically controlled reactions. Double stereodifferentiation under kinetic control conditions was successful, and the cyanation reaction occurred with complete syn diastereoselectivity using the matched pair. The versatility of the resulting amino nitrile as a synthetic intermediate was tested by performing the synthesis of orthogonally protected (R)-(2-aminomethyl)alanine.

A straightforward reaction sequence consisting of a Sonogashira coupling of protected propargylic amines, a cobaltcatalysed neutral Diels-Alder reaction, DDQ oxidation of the dihydroaromatic intermediate, a sodium borohydride reduction and an acid induced Friedel-Crafts-type cyclisation approach incorporating four simple starting materials leads to polyfunctionalised polycyclic products. Based on the electronic, steric and structural preconditions either seven-membered dibenzoazepine derivatives or alternatively six-or eight-membered isoindoline derivatives are formed.

[reaction: see text] The rhodium-catalyzed CH-insertion reaction of diazo ester derivatives into dihydroaromatic compounds was expanded to the application of various polysubstituted and functionalized 1,4-dienes generated from a cobalt-catalyzed Diels-Alder reaction. The highly regioselective CH-insertion process produces after DDQ oxidation polysubstituted, polyfunctionalized aromatic compounds in good overall yields.