Rh(II)-Catalyzed skeletal reorganization of 1,6- and 1,7-enynes through electrophilic activation of alkynes.

The skeletal reorganization of 1,6- and 1,7-enynes leading to 1-vinylcycloalkenes using Rh(II) as a catalyst is reported. Two possible isomers of 1-vinylcycloalkenes, type I and type II, can be obtained, the ratio of which are highly dependent on the substitution pattern of the enynes used. Formation of type I compounds involves a single cleavage of a C-C double bond, the product of which is identical to that of enyne metathesis.

Gold-catalyzed hydrative carbocyclization of 1,5- and 1,6-diyn-3-ones via an oxygen transfer process.

This study reports new hydrative carbocyclizations of 1,5- and 1,6-diyn-3-ones catalyzed by PPh3AuOTf, involving a pi-alkyne-assisted oxygen transfer in the reaction mechanisms. Treatment of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes with PPh3AuOTf (5 mol %) in wet 1,4-dioxane (23 degrees C, 10 min) led to hydrative aromatization to give 4-hydroxyl-1-naphthyl ketones efficiently. This approach is also extendible to the hydrative cyclization of acyclic 1,5-diyn-3-ones, which afforded 4-cyclopentenonyl ketones in reasonable yields.

The skeletal rearrangement of gold- and platinum-catalyzed cycloisomerization of cis-4,6-dien-1-yn-3-ols: pinacol rearrangement and formation of bicyclo[4.1.0]heptenone and reorganized styrene derivatives.

With gold and platinum catalysts, cis-4,6-dien-1-yn-3-ols undergo cycloisomerizations that enable structural reorganization of cyclized products chemoselectively. The AuCl3-catalyzed cyclizations of 6-substituted cis-4,6-dien-1-yn-3-ols proceeded via a 6-exo-dig pathway to give allyl cations, which subsequently undergo a pinacol rearrangement to produce reorganized cyclopentenyl aldehyde products. Using chiral alcohol substrates, such cyclizations proceed with reasonable chirality transfer.

Short and efficient synthesis of coronene derivatives via ruthenium-catalyzed benzannulation protocol.

[reaction: see text] TpRuPPh3(CH3CN)2PF6 (3 mol %) was very active in catalytic benzannulation of 1-phenyl-2-ethynylbenzenes in dichloroethane (60 degrees C, 36 h) to afford phenanthrene in 95% yield. This method is applicable to the synthesis of various polycyclic aromatic hydrocarbons via two- and four-fold benzannulations, including various substituted coronene derivatives (53-86% yields) using this catalyst at a moderate loading (10 mol %).