Display omitted
•Acid mediated cyclization of mixed acetals leading to functionalized thiophenes.•Synthesized in high over all yield up to 85% and characterized by spectral data.•These thiophenes are ...the novel building blocks for further exploration.
β-oxodithioates react with bromoacetaldehyde diethylacetal in the presence of anhydrous potassium carbonate in dimethyl formamide at 80°C to yield the corresponding mixed acetals. These acetals undergo smooth cyclization in the presence of ethanolic orthophosphoric acid to afford the corresponding 2-methylthio-3-acyl/aroyl/heteroaroyl thiophenes in 64–85% high overall yields.
A versatile and convenient one-pot direct approach to 2,3-disubstituted benzo/naphthobfurans via domino annulation of α-oxoketene dithioacetals and 1,4-benzo/naphthoquinone has been achieved in the ...presence of aluminium chloride at room temperature. This protocol represents an extremely simple, straightforward and rapid entry to highly substituted benzo/naphthobfurans in good yields from easily viable starting materials under mild reaction conditions.
Display omitted
Compounds incorporating 1,3-oxathiole moieties in their frameworks are biologically active. Active methylene ketones can be easily converted to the corresponding dithiocarboxylates by treatment with ...trithiocarbonate in the presence of sodium hydride. The reactions of aroyl dithiocarboxylates with α-haloketones such as phenacyl bromide or bromoacetone afford substituted 2-ylidene-1,3-oxathioles in good yields.
A facile one pot synthetic path for the preparation of pyrimidine-5-carbaldehydes from α-formylaroylketene dithioacetals is described. Amidines were allowed to react with α-formylaroylketene ...dithioacetals in DMF or acetonitrile to afford the pyrimidine-5-carbaldehydes. The starting compounds reported earlier were synthesized from α-oxoketene dithioacetals in excellent amount.
Display omitted
A novel synthesis of polysubstituted pyrazoles
3a–
d, pyrimidines
4a–
f and quinolines
5a–
c via the reaction of α,α-oxoketene dithioacetals
2a–
c with hydrazine hydrate, malonohydrazide, urea, ...thiourea and aniline is reported and the synthetic potential of the method is demonstrated. The structure of the new compounds was established upon their elemental analysis, IR,
1H NMR and
13C NMR.
The synthesis and reactivity of α-oxoketenes dithioacetals (S,S-acetals), general structure (R¹C=OC(R²)=C(SR³)(SR4), are reported. We also showed the application of S,S acetals as synthons for ...efficient synthesis of isoxazoles, pyrazoles, indazoles, thiophenes, dithiol thiones, pyridines, pyrimidines and other heterocycles. This work aims to review the importance of α-oxoketenes dithioacetals in organic chemistry during the past few years.
An efficient regiocontrolled synthesis of highly substituted and annulated indazoles involving base induced addition–elimination of 1,3-diphenyl-5-cyanomethylpyrazole to a variety of acyclic and ...cyclic α-oxoketene, followed by acid assisted cycloaromatization of the resulting conjugate adducts has been reported.
Graphic
1-Bis(methoxy)-4-bis(methylthio)-3-buten-2-one has been shown to be a useful three carbon synthon for efficient regiospecific synthesis of a variety of five (pyrazole and isoxazole) and six membered ...(pyrimidines, pyridone and pyridines) heterocycles with masked (or unmasked) aldehyde functionality by cyclocondensation with bifunctional heteronucleophiles such as hydrazine, hydroxylamine, guanidine, thiourea, cyanoacetamide and substituted β-lithioaminoacrylonitriles. Reaction of 1-bis(methoxy)-4-bis(methylthio)-3-buten-2-one with methylene iodide and Zn–Cu couple under Simmons–Smith reaction conditions afforded 2-(methylthio)thiophene-4-aldehyde in good yield, whereas cycloaromatization with thiophene-2- and 3-acetonitriles gave the corresponding substituted benzothiophene-4- and 7-aldehydes in good yields.
Graphic
Highly efficient regiospecific routes to potentially carcinogenic polycyclic aromatic hydrocarbons such as substituted benzo
cphenanthrenes, benzo
cfluorenes, 16,17-dihydro-11-methyl-15
Hcyclopenta
...aphenanthrene, 5-methyl-7,8,9,10-tetrahydrochrysene and 1,4-dimethylphenanthrene have been developed. The overall strategy involves our aromatic annulation protocol through base induced conjugate addition–elimination on the cyclic and acyclic α-oxoketene dithioacetals with the appropriate arylacetonitriles followed by acid induced cyclodehydration of the resulting conjugate adducts. Subsequent reductive dethiomethylation (Raney Ni) and dehydrogenation (DDQ) of the cyclized products affords the methyl substituted PAHs in high yields.
Graphic
PDF
