Synthesis and characterization of N-t-BOC protected pyrrole-sulfur oligomers and polymers

The synthesis and characterization of a new class of pyrrole-sulfur compounds is described. These compounds are designed to be precursors for an organic analogue of poly(sulfur nitride). Poly(N-t-BOC-2.5-pyrrolyl sulfide) was prepared from N-t-BOC-2,5-dibromopyrrole by first lithiating this compound with n-BuLi, followed by the addition of bis(p-tosyl) sulfide. Similarly, bis(N-t-BOC-2-pyrrolyl) sulfide was prepared starting from N-t-BOC-2-bromopyrrole. Subsequent selective oxidation with one or two equivalents of m-CPBA quantitatively gave bis(N-t-BOC-2-pyrrolyl) sulfoxide and -sulfone, respectively. Thermal deprotection of the t-BOC groups of the oligomers and the polymer resulted in decomposition of these compounds; the lauer is presumably due to a combination of sulfur-extrusion and polymerization

Novel thiophenes and method for polymerization of said thiophenes

The invention relates to novel thiophenes of formula (I) wherein R and R' are independently - hydrogen, alkyl or alkoxy or together a -O-(CH2)n-O bridge wherein n = 1 to 5. Said thiophenes are suitable for the production of polythiophenes which can be used as organic conductors

Well-defined oligo(pyrrole-2,5-diyl)s by the Ullmann reaction

The Ullmann coupling reaction has been used to polymerize N-t-BOC-2,5-dibromopyrrole into well-defined oligo(pyrrole-2,5-diyl)s. After optimization of the reaction conditions, i.e. using 1 wt equiv of Cu-bronze in DMF at 100 "C for 1 h, oligomers up to 25 repeating pyrrole units are obtained. Starting from 5,5‘- and 5,5"-dibrominated N-t-BOC protected bi- and terpyrrole as monomers, the polymerization is slower and a lower degree of polymerization is observed, yielding oligomers with an even lower molecular weight than those resulting from N-t-BOC-2,5-dibromopyrrole. The first 20 oligomers of poly(N-t-BOC-pyrrole)h ave been isolated by preparative HPLC. Characterization of the individual oligomers shows that they all are hydrogen terminated and possess a perfect 2,5-linkage: oligo(pyrro1e-2,5-diyl)s. The isolated oligomers have been used to study the optical and electrical properties of the oligomers as a function of chain length

Coplanarity by hydrogen bonding in well-defined oligoheterocycles

(Hetero)aryl-aryl coupling for covalent bonding and intramol. hydrogen bond formation for establishing the secondary structure have been united to design and construct well-defined, functionalized macromols. The suitability of azaheterocyclic units to realize this concept is exemplified by star shaped discotic liq. cryst. compds. and ladder-type conjugated copolymers. A review with >40 ref

Stereoselective reduction of benzoin by the NADH model 3-(dimethylcarbamoyl)-1,2,4-trimethyl-1,4-dihydropyridine

The Mg(ClO4)2-induced reduction of racemic benzoin by the racemic NADH model compound 3-(dimethylcarbamoyl)-1,2,4-trimethyl-1,4-dihydropyridine (1), in accordance to Cram's rule, leads exclusively to meso-1,2-diphenyl-1,2-ethanediol. However, while R-1 equally reduces 5-benzoin to afford meso-1,2-diphenyl-1,2-ethanediol, S-1 is reluctant to react with S-benzoin. The intermediacy of a strictly organized transition state, composed of chelated substrate, dihydropyridine and magnesium ion is involved

Facile synthesis of a chiral polymeric helix; folding by intramolecular hydrogen bonding

In a single condensation step, a polyureidophthalimide is synthesized, which folds into a chiral, helical architecture according to CD spectroscop