1,3-Dipolar cycloaddition ofin situ generated 2,2-dimethyl-and 2,2-dichlorodiazocyclopropanes to 3,3-dimethylcyclopropene

2,2-Dimethyl- and 2,2-dichlorocyclopropyl-N-nitrosoureas were synthesized for the first time. Under the action of MeONa/MeOH at ?10°C, these compounds generate the corresponding 2,2-dimethyl- and 2,2-dichlorodiazocyclopropanes, which are readily trapped by 3,3-dimethylcyclopropene to give the products of 1,3-dipolar cycloaddition,viz., isomeric substituted spiro(2,3-diazabicyclo[3. 1 .0] hex-2-ene-4,1 ′-cyclopropanes), in yields of about 70%,     

Synthesis and properties of novel bis(triarylamines) based on a 3,3'-diphenyl-2,2'-bithiophene core

An efficient synthesis of 3,3'-diphenyl-2,2'-bithiophene based bis(triarylamines) and their physical properties are reported.     

Molecular weight dependent charge carrier mobility in poly(3,3' '-dioctyl-2,2':5',2' '-terthiophene)

Poly(3,3' '-dioctyl-2,2':5',2' '-terthiophene), a polymer recently used for the fabrication of organic field effect transistors, has been fractionated into five fractions distinctly differing in their molecular weights (Mn), with the goal of determining the influence of the degree of polymerization (DPn) on its principal physicochemical parameters. It has been demonstrated that within the Mn range studied (from 1.5 kDa to 10.5 kDa by SEC), corresponding to DPn from 10 to 38, the polymer band gap steadily decreases with growing molecular weight, which is clearly manifested by an increasing bathochromic shift of the band originating from the pi-pi* transition. The same trend is observed for the HOMO level, determined from the onset of the p-doping in cyclic voltammetry, which shifts from -5.10 eV to -4.90 eV for the lowest and the highest molecular weight fractions, respectively. The most pronounced influence of DPn has been found for the charge carriers' mobility-one of the most important parameters of field effect transistors (FETs) fabricated from this polymer. A fourfold increase in DPn results in an increase of the carriers' mobility by more than 3 orders of magnitude. Comparison of these results with those obtained for fractionated regioregular poly(3-hexylthiophene) shows a strikingly similar behavior of both polymers with respect to the molecular weight.     

A novel efficient synthetic method for 2,2',3,3'-biphenyltetracarboxylic dianhydride

A novel approach to the synthesis of 2,2',3,3'-biphenyltetracarboxylic dianhydride is described. The target compound was prepared by a nickel-catalyzed coupling reaction of dimethy 3-chlorophthalate (3-DMCP) for 4 h at 70-80 C, followed by subsequent hydrolysis of tetra-ester in acid solution and dehydration of tetra-acid, with overall yield of 68%. The structures of the products were characterized by IR, 1H NMR and 13C NMR respectively.     

A novel efficient synthetic method for 2,2＇,3,3＇-biphenyltetracarboxylic dianhydride

A novel approach to the synthesis of 2,2',3,3'-biphenyltetracarboxylic dianhydride is described. The target compound was prepared by a nickel-catalyzed coupling reaction of dimethy 3-chlorophthalate (3-DMCP) for 4 h at 70-80℃, followed by subsequent hydrolysis of tetra-ester in acid solution and dehydration of tetra-acid, with overall yield of 68%. The structures of the products were characterized by IR, ¹H NMR and ¹³C NMR respectively.     

Helical sexithiophenes: an experimental and theoretical study implicating the alternating 2,2':3,3' regioisomer as a reliable helical motif

Perchlorinated sexithiophene regioisomer, 2,2' ' '-diX-5,5',5' ',5' ',5' ' ',5' ' '-hexachloro-[3,3';2',2' ';3' ',3' ';2' ',2' ' ';3' ' ',3' ' ']sexithiophene (compound 1), demonstrates a reliable helical conformation in the solid state, regardless of a broad range of substituents, X. The synthesis and composition of compound 1a (X = H) synthetically accommodates substituent diversity at the 2- and 2' ' '-sites. X-ray crystal structures (X = H, Cl, Br) and theoretical geometry optimizations (X = H, Cl, Br, I, Me, Et, t-Bu, and Ph) both confirm that the helical state, a conformation likely dictated by internal torsional strain, is predominant and unaffected by substituent X. It is predicted (ACID/B3LYP/6-31G(d) calculations and UV-visible spectra) that the helical structure exists as a fully conjugated system.     

Photoinduced electron-transfer bicyclopropenyl-benzene rearrangements of 2,2',3,3'-tetraphenylbicyclopropenyls: a new mechanism via Dewar benzene

[reaction: see text] The 9,10-dicyanoanthracene-sensitized photoreaction of 1-methyl- and 1,1'-dimethyl-2,2',3,3'-tetraphenylbicyclopropenyl gives the corresponding benzene and Dewar benzene derivatives, indicating that their photoinduced electron-transfer bicyclopropenyl-benzene rearrangements proceed via Dewar benzenes.