Modernized low pressure carbonylation methods in batch and flow employing common acids as a CO source.

Carbonylation reactions, such as Heck, Sonogashira, and radical carbonylations, were successfully carried out in a "two-chamber reactor" where carbon monoxide was produced ex situ by the Morgan reaction (dehydration of formic acid by sulfuric acid). By a subsequent application in a microflow system using a "tube-in-tube" reactor where gas-permeable Teflon AF2400 was used as the inner tube, it is demonstrated that formic acid/sulfuric acid can be employed concomitantly with an amine base such as triethylamine in the Heck aminocarbonylation of aryl iodide.

Rh-catalyzed [5+1] and [4+1] cycloaddition reactions of 1,4-enyne esters with CO: a shortcut to functionalized resorcinols and cyclopentenones.

We have developed novel Rh-catalyzed [n+1]-type cycloadditions of 1,4-enyne esters, which involve an acyloxy migration as a key step. The efficient preparation of functionalized resorcinols, including biaryl derivatives, from readily available 1,4-enyne esters and CO was achieved by Rh-catalyzed [5+1] cycloaddition accompanied by 1,2-acyloxy migration. When enyne esters had an internal alkyne moiety, the reaction proceeded by a [4+1]-type cycloaddition involving 1,3-acyloxy migration, leading to cyclopentenones.

Synthesis of functionalized resorcinols by rhodium-catalyzed [5+1] cycloaddition reaction of 3-acyloxy-1,4-enynes with CO.

A novel [5+1] type carbonylative cycloaddition reaction has been developed using a Rh complex as catalyst. This reaction can convert readily available 3-acyloxy-1,4-enynes and CO to a wide range of functionalized resorcinols in good yields. A mechanism involving Rh-catalyzed cyclocarbonylation of 3-acyloxy-1,4-enynes accompanied by a 1,2-acyloxy shift is proposed for the present [5+1] type cycloaddition reaction.

Preparation of fused polycyclic vinylcyclopropanes via radical cascade reactions.

Radical cascades employing (dichloromethyl)dimethylsilyl ethers as both a point of radical initiation and termination, allow efficient entry to fused polycyclic cyclopropanes, and are also suitable for the design of other radical processes terminated by beta-elimination of chloride.

Room temperature Au(I)-catalyzed exo-selective cycloisomerization of acetylenic acids: an entry to functionalized gamma-lactones.

A highly efficient gold-catalyzed cyclization reaction of various functionalized acetylenic acids is described. The cyclizations are conducted in the presence of Au(I) catalyst in acetonitrile at room temperature in a short reaction time. The reaction conditions are compatible with several functional groups, such as ester, alkene, alkyne, chloro, and free or protected alcohol, and lead to original gamma-lactones in good to excellent yields.