Thermally induced cyclopropene-carbene rearrangements: an overview

Formal (4+1) cycloaddition of methylenecyclopropanes with 7-aryl-1,3,5-cycloheptatrienes by triple gold(I) catalysis

7-Aryl-1,3,5-cycloheptatrienes react intermolecularly with methylenecyclopropanes in a triple gold(I)-catalyzed reaction to form cyclopentenes. The same formal (4+1) cycloaddition occurs with cyclobutenes. Other precursors of gold(I) carbenes can also be used as the C1 component of the cycloaddition.

Pd-Catalyzed ring-opening cross-coupling of cyclopropenes with aryl iodides

A palladium-catalyzed cross-coupling reaction of cyclopropenes with aryl iodides affords 1,3-butadiene products in good yields.

Formal C-H amination of cyclopropenes

A novel C(sp(3))-H amination of trimethylsilyl-substituted cyclopropenes is described. This C-H amination proceeds via a tandem regioselective ene reaction between cyclopropenes and azodicarboxylate to generate a hydrazodicarboxylate intermediate followed by its site-selective allylic transposition.

Strained small rings in gold-catalyzed rapid chemical transformations

Gold-catalyzed reactions, which have been widely explored over the past several years, are powerful tools in organic synthesis to access complex molecular frameworks, and some corresponding excellent reviews have been reported. However, little attention has been paid to summarize the reactions of strained small-ring-containing molecules catalyzed by gold. This critical review mainly puts its emphasis on the recent progress in the field of gold-catalyzed transformations of cyclopropyl-, cyclopropenyl-, epoxy- and aziridinyl-containing molecules. The rapid construction of interesting building blocks in organic synthesis from strained small rings catalyzed by gold has been summarized in this review (106 references).

Recent developments of cyclopropene chemistry

This critical review discusses recent developments in the field of cyclopropene chemistry. Although several excellent reviews that mainly focused on the thermolysis and pyrolysis as well as metal-mediated reactions of cyclopropenes have been published, significant new developments have also been achieved in recent years. This brand new review provides an overview of the progress from 2007 to 2011 on the syntheses and transformations of cyclopropenes as well as their related mechanistic studies (238 references).

Experimental and theoretical investigation into the gold-catalyzed reactivity of cyclopropenylmethyl acetates

Cyclopropenylmethyl acetates have been shown to undergo rapid and stereoselective gold catalyzed rearrangement to Z-acetoxydienes in high yield. DFT calculations have shown that while several reaction pathways can be envisaged only a single, ring-opening one operates.

Cyclopropenation of alkylidene carbenes derived from alpha-silyl ketones

A new cyclopropanation reaction involving Calpha-Si bond insertion of alkylidene carbenes derived from alpha-silyl ketones has been developed. This unprecedented alkylidene carbene reactivity features excellent selectivity for insertion into Calpha-Si bonds rather than insertion into Cgamma-H bonds or addition to gamma,delta-double or -triple bonds. The selectivity trend clearly indicates that the alpha-oxygen in the tether significantly promotes Cgamma-H insertion, although the Calpha-Si bond insertion still competes effectively.

Highly substituted 2-amido-furans from Rh(II)-catalyzed cyclopropenations of ynamides

Rh(II)-catalyzed cyclopropenations of ynamides are described. Although an actual amido-cyclopropene intermediate may not be involved, these reactions provide a facile entry to highly substituted 2-amido-furans, thereby formerly constituting a [3 + 2] cycloaddition. An application of these de novo 2-amido-furans in N-tethered intramolecular [4 + 2] cycloadditions is also illustrated, leading to dihydroindoles and tetrahydroquinolines.