Patrick R. Huddleston

Synthesis and optical storage properties of a thiophene-based holographic recording medium

The results of the fabrication and optical data storage characteristics of a novel azothiophene polyester 9 for potential holographic storage are reported. The polyester is derived from an azothiophene diol 1 and diphenyl phthalate 8via in vacuo melt transesterification. Inclusion of a 5-methoxy-2-thienyl moiety generates a trans π–π* transition centered close to 405 nm. An investigation of the optical data storage characteristics of a solution cast film of azopolyester with a thickness of 65 µm is summarised. The optical anisotropy induced by a 532 nm frequency doubled YAG laser and probed at a wavelength of 633 nm outside the absorption band with a polarimeter reveals a very high induced anisotropy of 7 rad (laser intensity, 250 mW cm−2). The calculated birefringence of the film is 0.02 per micron. Maximum anisotropy is reached after approximately 70 s of irradiation. The induced anisotropy disappears at approximately 90 °C. Room temperature stable gratings can be inscribed with high diffraction efficiency.

AN EASY SYNTHESIS OF 3-AMINO- AND 3-NITROTHIOPHENE

Abstract 3-Amino- and 3-nitrothiophene are readily made by the decarboxylation of the corresponding thiophene-2-carboxylic acids which are easily prepared from the commercially available methyl 3-aminothiophene-2-carboxylate.

Preparation and some reactions of substituted thieno[3,4-b]furans

Treatment of a variety of 3-hydroxythiophenes with either an excess of methyl or ethyl bromoacetate and anhydrous potassium carbonate in acetonitrile under reflux, or in DMSO at room temperature, gave the 3-alkoxy derivatives in good to excellent yields. Utilization of the Dieckmann condensation, using either sodium alkoxide–alcohol or sodium hydride–benzene as base, afforded substituted thieno[3,4-b]furans in moderate to good yields. These compounds were found to exist predominantly in either the keto or enol form dependant upon the nature of substitution in the thiophene ring. Derivatives prepared from thieno[3,4-b]furan compounds showed that the system exhibited the chemical properties associated with ketones, enols, and β-keto esters. In addition the allyl ether was formed from 3-hydroxy-2,4-bismethoxycarbonylthieno[3,4-b]furan which underwent the Claisen rearrangement upon distillation.

A RAPID CONVERSION OF 3-OXOTHIOLANES INTO 3-AMINOTHIOPHENES

ABSTRACT 3-Oxotetrahydrothiophenes can be rapidly converted into 3-aminothiophenes by refluxing with hydroxylamine hydrochloride in a polar solvent, usually acetonitrile.

Dehalogenation of 1-halogenothienyl-di- and -tetra-hydroisoquinolines by sodium methoxide in dimethyl sulphoxide

On treatment with sodium methoxi-dimethylsulphoxide (NaOMe–DMSO) 1-(5-halogeno-2-thienyl)-6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinolines suffer loss of halogen and are converted into the related 1-hydroxytetrahydroisoquinolines. The reaction fails with comparable 1-bromophenyl- and 1 -(halogeno-3-thienyl)tetrahydroisoquinolines. A similar transformation takes place with (5-halogeno-2-thienyl)phenylmethoxymethanes, leading to the dimethyl acetal of the 5-dehalogenated-2-thienyl phenyl ketone. α-Halogenated-2- and 3-thienyl-3,4-dihydroisoquinolines undergo dehalogenation-aromatisation with NaOMe–DMSO. Mechanisms for these conversions are proposed.

Preparation and reactions of 2,5-dimethoxythiophen

2,5-Dimethoxythiophen, prepared from 2,5-di-iodothiophen, undergoes some electrophilic substitution reactions but is susceptible to ring opening by mineral acid. It is also decomposed by butyl-lithium. Reaction with maleic anhydride in xylene proceeds with extrusion of sulphur and a second Diels–Alder reaction to give a bis-adduct (2).

Thienyl analogues of the alkaloids. Part II. 3-Thienyl analogues of ephedrine and ψ-ephedrine

The synthesis, from 3-propionylthiophen, of the 3-thienyl analogues of ephedrine and ψ-ephedrine, and the resolution of the latter are described. An account is also given of alternative approaches to these isosteres from 2,5-dichloro- and 2,5-dibromo-3-propionylthiophen.

3,3′-Azothiophene

Methyl 3-nitrothiophene-2-carboxylate was reduced with bismuth(III) chloride/potassium borohydride to give an unstable hydroxylamine which was oxidised without isolation using iron(III) chloride to give methyl 3-nitrosothiophene-2-carboxylate. Condensation of this with methyl 3-aminothiophene-2-carboxylate furnished the azodiester. This was more conveniently obtained by manganese dioxide oxidation of the aminoester. Hydrolysis of the azodiester to give the diacid followed by decarboxylation gave 3,3′-azothiophene which could be oxidised to 3,3′- azoxythiophene with hydrogen peroxide. The azodiester was oxidised to the corresponding azoxydiester with urea-hydrogen peroxide/trifluoroacetic anhydride and reduced to the related hydrazothiophenediester with diimide.

Nitration of methyl-3-hydroxy- and 5-methyl-3-hydroxy-thiophene-2-carboxylate, and some chemistry of the products

The nitration of methyl-3-hydroxythiophene-2-carboxylate furnishes two products, the lower melting of which was previously thought to be the 4- (3) and the other the 5-isomer (2); these assignments have been reversed on the basis of carbon-13 NMR. data and the revised structures have been confirmed both by O to N acyl migrations and by the preparation of the first examples (20) and (23) of the thieno[3,4-b][1,4]oxazine ring system from derivatives of the 4-nitro isomer.

A SYNTHESIS OF 2-ACYL-3-HYDROXYTHIOPHENES

Abstract 2-Acyl-3-hydroxythiophenes have been made by the reaction of the anion of a mercaptoketone with dimethyl acetylenedicarboxylate to give a hydroxythiophene ester which is then hydrolysed and decarboxylated.