The preparation of an advanced intermediate toward the enantioselective synthesis of tetrodotoxin is outlined. The enantiomerically pure cyclopentene 15 was generated from ketone 14 by alkylidene carbene insertion with retention of absolute configuration. An ozonolysis/aldol sequence first produced the trans cyclohexenone, which upon epimerization gave the more stable cis enone 18.

A simple and efficient metal-free methodology for the regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles has been developed by applying a novel inverse electron-demand-1,3-dipolar cycloaddition approach. The practical one-pot metal-free strategy can be accomplished with various alkylidene malononitriles and aromatic azides in the presence of base.

Organocatalysts containing primary-secondary diamines based on bispidine have been developed to catalyze the asymmetric Michael addition of ketones to alkylidene malonates and nitroalkenes. The corresponding products were obtained in high yields (up to 99%) with high diastereoselectivities (up to 99:1) and high enantioselectivities (up to 97% ee) under mild conditions using either environmental...

meso-Alkylidene (m-benzi)pentaphyrin containing exocyclic C=C double bonds at two meso-positions is synthesized and fully characterized for the first time. The single crystal X-ray crystallographic analysis shows a concave conformation with two pyrrole rings inverted. The first protonation occurs exclusively at core nitrogen. The synthesized compound displays concentration dependent chromogenic...

The asymmetric direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactams with alkylidene malonates has been developed. Various 5-substituted 3-pyrrolidin-2-ones were obtained in high yields (up to 93%) with excellent stereoselectivities (up to 94% ee, 95 : 5 dr), using a novel bifunctional C(1)-symmetric guanidine organocatalyst embodied a secondary amine subunit.

The ring closing enyne metathesis reaction (RCEYM) catalyzed by molybdenum based monoalkoxy pyrrolyl Schrock type catalysts has been studied by means of DFT (B3LYP-D) calculations. The two potential active alkylidene species as well as the three proposed reaction mechanisms (ene-then-yne, endo-yne-then-ene and exo-yne-then-ene) have been taken into account. Moreover, the influence on the exo- a...

The preparation of the crystalline amide 2 is reported. Conjugate addition to 2 proceeded with the expected high diastereocontrol to give 3. This set the stage for subsequent intramolecular alkylidene C-H insertion to give, after ozonolysis and aldol condensation, (-)-mesembrine 1. Amide 2 should be a useful chiron for the enantioselective construction of cyclic quaternary centers.

A highly enantioselective organocatalytic vinylogous aldol-cyclization cascade reaction of 3-alkylidene oxindoles to isatins has been achieved by using bifunctional organocatalysts. The unexpected intramolecular lactonization which follows the initial aldol reaction, leading to the cleavage of the oxindole ring and generation of enantioenriched spirooxindole dihydropyranones in good to excellen...