Chad A. Snyder

Synthesis, Characterization, and Structure of Some New Substituted 5,6-Fused Ring Pyridazines

Abstract Pyridazines are an important class of heterocyclic compounds as a result of their materials and commercial applications. The synthesis of 5,6-fused ring pyridazines 2a–h from 1,2-diacylcyclopentadienes (fulvenes) 1a–h is described herein. This route was quite general, and features an efficient and convenient two-step synthesis of a series of 5,6-fused ring 1,2-disubstituted pyridazines using enolized 1,2-disubstituted fulvenes in a methanolic solution of hydrazine. Full characterization of newly formed fulvene 1e and pyridazines 2a–h are reported. Single-crystal X-ray analysis confirms the molecular structure of pyridazine 2f, which displayed the expected pyridazine fused to the cyclopentadienyl moiety. Adding to their real world capabilities in electronic devices, compounds 2a–h display reasonably high stability in solution and in air at room temperature.

Direct analysis in real time mass spectrometry of fused ring heterocyclic organometallic compounds

Direct analysis in real time (DART) was able to desorb/ionize a series of fused-ring heterocyclic organometallic compounds to allow molecular analysis using a linear ion-trap mass spectrometer. Limited data is available pertaining to the use of ambient ionization with organometallic compounds but the developed analytical method allowed direct sampling of solutions prepared from pure organometallic compounds in dichloromethane to generate signals in the positive mode. A protonated molecule was detected (even when a charged ring structure was present) but signal intensity was dependent on the organometallic compound with respect to the specific metal–ligand interaction of the molecule as well as the helium gas temperature in the DART ion source. In addition, dimer formation for compounds was also observed. Tandem mass spectrometry was also possible to verify the tricarbonyl groups from the organometallic compound and show relative differences with respect to metal coordination. The desorption/ionization of these heterocyclic organometallic compounds with DART potentially gives synthetic chemists another ionization choice for rapid reaction product monitoring.

Synthesis and structure of some group VII 1,2-diacyl cyclopentadiene complexes and their pyridazine derivatives

A series of 1,2-diacyl cyclopentadienyl tricarbonyl manganese and rhenium complexes, [M(CO)3{η5-1,2-C5H3(CO-(R)2}] (3a–c and 4a–b), were isolated utilizing a straightforward, 3-step route. The synthetic pathway began with a 1,2-diacyl cyclopentadiene (fulvene), followed by the formation of its corresponding thallium salt and transmetallation with the appropriate pentacarbonyl metal bromide. X-ray crystallographic analysis and high-accuracy mass spectrometry confirmed the structures of the both the 4-methoxyphenyl and 4-chlorophenyl diacyl rhenium complexes, [Re(CO)3{η5-1,2-C5H3(CO-(4-OCH3)C6H4)2}] (4a) and [Re(CO)3{η5-1,2-C5H3(CO-(4-Cl)C6H4)2}] (4b). Diacyl complexes 3a–c and 4a–b were then ring-closed with hydrazine hydrate to form their corresponding pyridazine complexes, [M(CO)3{η5-1,2-C5H3(1,4-(R)2N2C2}] (5a–c and 6a–b), in good yields (60–83%). The pyridazyl ligands were found to be relatively labile, and recrystallization of the target complexes 5a–c and 6a–b afforded only the free pyridazine ligands.

The synthesis, characterization, and structure of a series of 4H-thieno[3,4-c]pyrroles and their corresponding pyrrolium cyanoborohydride salts

A general, convenient route toward N-substituted 5,6-dihydro-4H-thieno[3,4-c]pyrroles was accomplished by the reductive amination of 2,5-dimethylthiophene-3,4-dicarbaldehyde with various primary amines in a solution of sodium cyanoborohydride and methanol/acetic acid (80–88% yield). For the N-alkyl cases, the product isolated was the cyanoborohydride salt of the desired product, 1,3-dimethyl-5-alkyl-5,6-dihydro-4H-thieno[3,4-c]-5-pyrrolium cyanoborohydride. For the aryl case employing aniline, the desired free pyrrole, 1,3-dimethyl-5-phenyl-5,6-dihydro-4H-thieno[3,4-c]pyrrole, was isolated. X-ray crystallographic analysis of both the N-propyl and N-phenyl trials confirmed the salt and free amine nature of the products. GRAPHICAL ABSTRACT

Synthesis and Characterization of Some Thallium Cyclopentadienide Fused Ring Pyridazines

Abstract Thallium cyclopentadiene (Cp) salts are important precursors for the synthesis of a variety of compounds having materials and commercial applications. The synthesis of 5,6-fused ring thallium Cp pyridazines 2a–d from previously reported 5,6-fused ring pyridazines is described herein. This route was quite general, and features an efficient and convenient two-step synthesis of a series of TlCp salts in a THF solution of thallium ethoxide. Full characterization of newly formed TlCp salts 3a–d are reported. GRAPHICAL ABSTRACT

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).