One-pot desulfurative-fluorination-bromination. Synthesis of 2,5-dibromo-3-(1,1-difluoroalkyl)thiophenes.

A unique one-pot, high-yield desulfurative-fluorination-bromination reaction which leads to the synthesis of 2,5-dibromo-3-(1,1-difluoroalkyl)thiophenes is reported. A single dithiolane reactant can be used to produce both 2,5-dibromo-3-(1,1-difluoroalkyl)thiophene and 3-(1,1-difluoroalkyl)thiophene with longer alkyl chains.

Second-harmonic generation in resonant waveguide gratings incorporating ionic self-assembled monolayer polymer films.

Experimental results on resonantly excited second-harmonic generation (SHG) in a periodic ionically self-assembled monolayer (ISAM) film are reported. A double-layer guided-mode resonance filter (GMRF) structure is coated with 40 bilayers of pyrlium-based chi(2) ISAM thin film and excited with the fundamental of a Nd:YAG laser. Enhanced second-harmonic conversion in the ISAM film is achieved because of the local field enhancement associated with the fundamental resonating leaky mode.

Synthesis and solid-state structures of dimethyl 2,2'-bithiophenedicarboxylates.

The syntheses of dimethyl 2,2'-bithiophene-4,4'-dicarboxylate (3), dimethyl 2,2'-bithiophene-3,4'-dicarboxylate (4), and dimethyl 2,2'-bithiophene-3,3'-dicarboxylate (5) are described. Single-crystal X-ray structural analysis of these compounds shows that the thiophene rings in 3 and 4 are nearly coplanar (dihedral angle close to 0 degrees ) and they adopt the anti sulfur conformation in the solid state. Further, the structure of 4 is in agreement with our previous suggestion that there is an electrostatic stabilization of the planar structure due to attraction of the 3-carbonyl oxygen to the sulfur of the distal ring.