Nathan C. Tice

Synthesis and Self-Assembly of Glycal-Based Bolaforms

Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain alpha,omega-diol, followed by deacetylation under Zemplen conditions. The reactions are stereoselective and preferentially afford the alpha-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key intermolecular interactions between bolaform headgroups are necessary to determine the structure in the solid state. The diversity and differentiation of the functional groups present in glycal-based bolaforms suggest that they could be useful probes of the various noncovalent forces controlling the structure of new nanomaterials.

Synthesis and structure of 5,7-dimethylthieno〔3,4-d〕pyridazine

The reaction of 2,5-dimethylthiophene-3,4-dicarboxaldehye (3) with excess hydrazine hydrate afforded the desired 5,6-fused ring thiophene derivative, 5,7-dimethylthieno[3,4-d]pyridazine (4), in high yield (82%). Pyridazine 4 was characterized spectroscopically and its structure was confirmed by X-ray crystallography. Compound 4 was observed to have an inverted, coplanar stacking arrangement in the solid state.

The unexpected formation and structure of 4,6-dimethylthieno〔3,4-c〕thiophene-1(3H)-thione

The reaction of 2,5-dimethylthiophene-3,4-dicarboxaldehye (1) with excess Lawessons Reagent afforded the unexpected 5,5-fused ring thienothione derivative, 4,6-dimethylthieno[3,4-c]thiophene-1(3H)-thione (2), in good yield (79%). The desired non-classical thiophene, 1,3-dimethylthieno[3,4-c]thiophene (3), was observed by GC/MS as a minor product (approximately 5%) along with thione 2. The thienothione 2 was characterized spectroscopically and its structure was confirmed by X-ray crystallography. The formation of compound 2 is proposed to occur through a 1,3-hydride shift.

An Improved Route to Substituted Cyclopenta[c]thiophenes: Synthesis of 5-Alkyl-1,3-dimethyl-4H-cyclopenta[c]thiophenes and Sulfone Ester Precursor

Abstract An improved route to substituted cyclopenta[c]thiophenes was accomplished by treating 1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene-5-one (1) with alkyl Grignard reagents to obtain the 5-alkyl-1,3-dimethyl-4H-cyclopenta[c]thiophenes, 5-methyl-1,3-dimethyl-4H-cyclopenta[c]thiophene (2) and 5-ethyl-1,3-dimethyl-4H-cyclopenta[c]thiophene (3), in good yield (60% and 65%, respectively). An important cyclopenta[c]thiophene precursor, 5-carbomethoxy-5-phenylsulfonyl–1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene (9) was synthesized, in an alternate route, by treating 3,4-bis(chloromethyl)-2,5-dimethylthiophene (7) with methyl phenyl sulfonyl acetate (8).