Periselectivity in the aza-Diels-Alder Cycloaddition between α-Oxoketenes and -(5-Pyrazolyl)imines: A Combined Experimental and Theoretical Study.

The thermal 6π aza-Diels-Alder cycloadditions between α-oxoketenes, derived from a thermally induced Wolff rearrangement of 2-diazo-1,3-diketones, and -(5-pyrazolyl)imines as prototypical electron-rich 2-azadienes lead to two distinct sets of products, essentially as a function of the nature of the α-oxoketenes involved. For instance, cyclic five-membered α-oxoketenes lead preferentially to spiro hydropyridin-4-ones, which involves the α-oxoketenes as the 2π partners at their C═C double bond and the -(5-pyrazolyl)imines as the 4π partners at their 2-azadiene moiety. In contrast, other cyclic and acyclic α-oxoketenes lead preferentially to 1,3-oxazin-4-ones, which now involves the α-oxoketenes as the 4π partners at their 1-oxadiene moiety and the -(5-pyrazolyl)imines as the 2π partners at their C═N double bond.

Crystal structure of ethyl ()-2-cyano-3-(thio-phen-2-yl)acrylate: two conformers forming a discrete disorder.

In the title compound, CHNOS, all the non-H atoms, except for the ethyl fragment, lie nearly in the same plane. Despite the mol-ecular planarity, the ethyl fragment presents more than one conformation, giving rise to a discrete disorder, which was modelled with two different crystallographic sites for the eth-oxy O and eth-oxy α-C atoms, with occupancy values of 0.5.

Oligo p-Phenylenevinylene Derivatives as Electron Transfer Matrices for UV-MALDI.

Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications in the growing field of organic electronics. Yet, PVs are also versatile molecules, the optical and physicochemical properties of which can be tuned by manipulation of their structure. We report the synthesis, photophysical, and MS characterization of eight PV derivatives with potential value as electron transfer (ET) matrices for UV-MALDI.