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Intramolecular heterocyclization of (Z)-5-(2-hydroxyethyl)-3-methyl-4-oxothiazolidines,
bearing electron-withdrawing groups conjugated to an exocyclic double bond at C(2)-position, afforded under reductive conditions, not easily accessible cis-tetrahydrofuro[2,3-d]thiazole derivatives. The reactions of these functionalized push-pull β-enamines occur in a stereocontrolled fashion via activated vinylogous N-methyliminium ions, which are trapped by an internal hydroxyethyl group.
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We recently described a series of catalysts bearing a hydroxyl group in close proximity to a basic amine which effect the methanolysis of para-nitrophenyl (PNP) esters.1 These catalysts, an example of which is provided in Scheme 1, operate by an Onucleophilic mechanism in which the hydroxyl group of the
catalyst (1) undergoes base-catalyzed acylation by the PNP ester (2) to give an acyl-transferred intermediate (3). This intermediate then undergoes base-catalyzed deacylation to provide the product (4) and regenerate the catalyst (1).
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Benzotriazole reagents for thioacylation (RCSBt), thiocarbamoylation (RR'NCSBt), aryl/alkoxythioacylation
(ROCSBt), and aryl/alkylthiothioacylation (RSCSBt) are synthesized, and their utility
assessed by syntheses of representative heteroaryl thioureas 3a–g, thioamides 15a–s, thionoesters 16a–
h, thiocarbamates 17a–e, dithiocarbamates 18a–d, thiocarbonates 19a–c, and dithiocarbonates 20a–c.
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The ligand di-2-pyridylketone azine (1) was prepared by reaction of di-2-pyridylketone with hydrazine hydrate. This potentially hexadentate compound incorporates two extra imine donor atoms over other, previously investigated, ligands derived from di-2-pyridylmethane. The coordination chemistry of 1 was investigated with silver nitrate, copper nitrate and palladium chloride.
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Accurate, low temperature X-ray crystal structure determinations show that 3,3’-biquinoline (6), 2,2’-biquinazoline (7), 2,2’-biquinoxaline (8), 2,2’-bibenzoxazole (10) and 2,2-bibenzothiazole (11) all exist in the solid state in centrosymmetric, planar conformations that minimise their dipole moments and maximise both conjugation between the rings and various types of attractive intermolecular associations. In contrast, 4,4’-biquinazoline (9) and 1,1’-bibenzotriazole (12) display non-planar conformations due to repulsive intramolecular interactions.
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The potential of the directional non-bonded 1,5-type S···O interactions to initiate an incipient stage of an in situ rearrangement of N-unsubstituted thiazolidine enaminones to the functionalized 1,2-dithioles has
been demonstrated. Spectral characteristics, as well as an X-ray structural analysis of the selected rearranged product, indicate that a dynamic interconversion occurs in a solution between the 1,2-dithiole and 3,3aλ⁴,4-trithia-1-azapentalene bicylic form.
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A family of six Donor-Acceptor-Donor (D-A-D) monomers was synthesized using combinations of thiophene, 3,4-ethylenedioxythiophene (EDOT) and 3,4-ethylenedioxypyrrole (EDOP)
as donor moieties, and cyanovinylene as the acceptor moiety, in order to understand the effects of modified donor ability on the optoelectronic and redox properties of the resulting electropolymerized materials. Spectroelectrochemistry indicated band gaps (Eg) ranging from 1.1 eV to 1.6 eV as donor quality increased and these values were confirmed by differential pulse voltammetry (DPV) and cyclic voltammetry (CV).
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The first metal complexes of 2,5-di(2-pyridyl)thiazolol[5,4-d]thiazole (5) are described. X-Ray crystal structures are reported for the free ligand 5, a dinuclear copper complex 6 and the two diastereoisomers, 7meso and 7rac, of the dinuclear bis(2,2’-bipyridine)ruthenium complex. The two diastereoisomers of 7 and the 4,4’-dimethyl-2,2’-bipyridine analogue 8 are readily separated by cation exchange chromatography.
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Regioselective addition of allylmercaptan at the C-3 position adjacent to the nitrogen
carrying phenyl group of the 1,4-phenylenediamine moiety of 1−4 was rigorously
confirmed by the 1D NOE difference in combination with gHMBC experiments. The
structures of 1,4-phenylenediamines 1−4, allylsulfanyl-N1-alkyl-N4-phenyl-1,4-
phenylenediamines 5−8, and cyclization products 9−14 were completely analyzed in both
CDCl3 and DMSO-d6 solutions.
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The allyllithium, generated from 1-[(2EZ)-3-chloroprop-2-enyl]-1H-1,2,3-benzotriazole (5) and
LDA in the presence of HMPA, reacts with enolizable and nonenolizable carbonyls solely at the
CCl terminus to give 1-(2-oxiranylvinyl)benzotriazoles 6a−g in 61−82% yields. Allyllithiums
generated from 6a,c reacted exclusively at the CBt terminus to give 10a−d in 68−88% yields.
Acidic hydrolysis of (oxiranylvinyl)benzotriazoles 6a−g and 10a−d provided 4-hydroxyalk-2-
en-1-one derivatives 12a−c,e,g, 13a−d and furan 14 in 41−86% yields.
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