Synthesis of functionalized maoecrystal V core structures.

Two strategies toward the total synthesis of maoecrystal V (1) culminating in the construction of core structures 2 and 3 are described.

On the mechanism of the palladium catalyzed intramolecular Pauson-Khand-type reaction.

Density functional theory calculations and experimental studies have been carried out on the intramolecular Pauson-Khand-Type reaction mediated by a PdCl(2)-thiourea catalyst, which proceeds under mild reaction conditions and provides a useful alternative to traditional Pauson-Khand reactions. The classical mechanism of the Pauson-Khand reaction involving the alkyne/alkene C-C bond formation as the key step has been found to be energetically unfavorable and is not in line with the experimental observations. A novel reaction mechanism has been proposed for the reaction.

Formal total synthesis of N-methylmaysenine.

A novel synthetic approach for the formal total synthesis of N-methylmaysenine (1) has been developed. Key steps involve the Ti-mediated vinylogous Mukaiyama aldol reaction of chiral ketene silyl N,O-acetal with beta-dithiane-substituted aldehyde, an aldol condensation, and a ring-closing metathesis reaction.

Synthetic study of 1,3-butadiene-based IMDA approach to construct a [5-7-6] tricyclic core and its application to the total synthesis of C8-epi-guanacastepene O.

An efficient intramolecular Diels-Alder (IMDA) strategy for the construction of the [5-7-6] tricyclic core (18) of guanacastepenes has been developed from cis- and trans-1,3-butadiene-tethered 4-oxopent-2-ynoic acid ethyl esters 10 and 11. This method facilitates the synthesis of C8-epi-guanacastepene O (36) in a very efficient manner.

Thioureas as ligands in the pd-catalyzed intramolecular Pauson-Khand reaction.

[reaction: see text] The thiourea-Pd complex was established as a novel type of catalyst in the PKR of allylpropargylamine, and the demonstrated chemistry may prove to be valuable for developing thiuorea as a ligand for the Pd-catalyzed Pauson-Khand reaction.

A highly efficient synthesis of the FGH ring of micrandilactone A. Application of thioureas as ligands in the Co-catalyzed Pauson-Khand reaction and Pd-catalyzed carbonylative annulation.

The functionalized FGH ring system of micrandilactone A was successfully constructed in high selectivity and good yields. The key reactions in our strategy are the Co-thiourea-catalyzed stereoselective, intramolecular Pauson-Khand reaction and Pd-thiourea-catalyzed stereoselective, intramolecular annulation. [structure: see text]

Tetramethyl thiourea/Co2(CO)8-catalyzed Pauson-Khand reaction under balloon pressure of CO.

A Pauson-Khand type of conversion of enynes to bicyclic cyclopentenones employing the commercially available Co2(CO)8 and tetramethylthiourea (TMTU) as catalysts is described. This method allows a variety of enynes with diverse functional groups to be cyclized into cyclopentenones of interest. [reaction: see text]