Recyclable heterogeneous metal foil-catalyzed cyclopropenation of alkynes and diazoacetates under solvent-free mechanochemical reaction conditions.

Silver and copper foil were found to be effective, versatile and selective heterogeneous catalysts for the cyclopropenation of terminal and internal alkynes under mechanochemical reaction conditions. This methodology enables the functionalization of a wide range of terminal or internal alkynes under ambient, aerobic, and solvent-free conditions. Finally, we have demonstrated a unique and versatile one-pot domino Sonogashira-cyclopropenation mechanochemical reaction for the formation of complex cyclopropenes.

Cyclopropenation of internal alkynylsilanes and diazoacetates catalyzed by copper(i) N-heterocyclic carbene complexes.

Copper(i) N-heterocyclic carbene (CuNHC) complexes are more catalytically active than traditional transition metal salts for the cyclopropenation of internal alkynylsilanes and diazoacetate compounds. A series of 1,2,3-trisubstituted and 1,2,3,3-tetrasubstituted cyclopropenylsilane compounds were isolated in good overall yields. An interesting regioselective and chemodivergent reaction pathway was also observed to furnish a tetra-substituted furan for an electron-rich donor/acceptor diazoacetate.

An inexpensive and recyclable silver-foil catalyst for the cyclopropanation of alkenes with diazoacetates under mechanochemical conditions.

The diastereoselective cyclopropanation of various alkenes with diazoacetate derivatives can be achieved under mechanochemical conditions using metallic silver foil and a stainless-steel vial and ball system. This solvent-free method displays analogous reactivity and selectivity to solution-phase reactions without the need for slow diazoacetate addition or an inert atmosphere. The heterogeneous silver-foil catalyst system is easily recyclable without any appreciable loss of activity or selectivity being observed.

Efficient and regioselective nickel-catalyzed [2 + 2 + 2] cyclotrimerization of ynoates and related alkynes.

A nickel-based catalytic system has been developed for [2 + 2 + 2] cyclotrimerization of various alkynes, especially ynoates. This catalytic system enables facile construction of substituted aromatic compounds in excellent yields with high regioselectivity.

Highly selective synthesis of tetra-substituted furans and cyclopropenes: copper(I)-catalyzed formal cycloadditions of internal aryl alkynes and diazoacetates.

A convenient Cu(I)-catalyzed cycloaddition of electron rich internal aryl alkynes and diazoacetates was discovered for the chemoselective and regioselective synthesis of tetra-substituted furans and cyclopropenes in moderate isolated yields (18-67%), and alkyne conversion (29-73%).

Cardiogenic arterial thromboembolism causing non-ambulatory tetraparesis in a cat.

A 1-year-old oriental cat was presented with a peracute onset of tetraparesis and vocalisation. Clinical findings were suggestive of multi-site thromboembolic disease, and this was confirmed on post-mortem examination. An echocardiogram showed severe restrictive cardiomyopathy and spontaneous echogenic contrast.

Balance between allylic C-H activation and cyclopropanation in the reactions of donor/acceptor-substituted rhodium carbenoids with trans-alkenes.

Rhodium(II)-catalyzed reactions of aryldiazoacetates with (E)-aryl-substituted alkenes generate C-H insertion products and/or cyclopropanes. The product distribution is influenced by the nature of the donor group on the carbenoid, the structure of the (E)-aryl-substituted alkenes, and the rhodium catalyst.

Evaluation of six-lead electrocardiograms obtained from dogs in a sitting position or sternal recumbency.

Objective: To compare 6-lead ECG traces in clinically normal conscious dogs in a sitting position and sternal recumbency to that of right lateral recumbency.

Animals: 31 healthy dogs with no history of cardiac disease.

Procedure: Six-lead ECGs were recorded for dogs in right lateral recumbency, a sitting position, and sternal recumbency.