Oxoketene Dithioacetals Research Articles

ChemInform Abstract: Oxoketene Dithioacetals as Versatile Synthones for Alternative 1,3‐ to 1,11‐Carbonyl Transpositions: A New Polyene Synthesis.

AbstractThe heptatrienals (II) are coupled with the aryl methyl ketones (I) to yield the octatetraenyl ketones (III) which are reduced, forming the corresponding alcohols (IV).

ChemInform Abstract: Cyclocondensation of Oxoketene Dithioacetals with 3‐Aminopyrazoles: A Facile Highly Regioselective General Route to Substituted and Fused Pyrazolo(a)pyrimidines.

AbstractCyclocondensation of the aminopyrazole (I) with dithioacetals such as (II), (IV), or (VII) gives rise to title compounds such as (III), (V), or (VIII), (IX).

ChemInform Abstract: Darzen′s Reaction on Oxoketene Dithioacetals: New Versatile Synthesis of Substituted and Anellated Furan‐2‐carboxylates.

AbstractDarzen's condensation of in situ formed lithiobromoacetate (see condition A)) with oxoketene dithioacetals such as (I) affords the title furans (II) which can be desulfurized to (III).

Studies on cycloaddition reactions of 1,3-diphenyl-2-azaallyl lithium and ethyl (benzylideneamino) acetate anion with α-oxoketene dithioacetals

The α-oxoketene dithioacetals undergo anionic [1,3] cycloaddition with l,3-diphenyl-2-azaallyllithium to give either pyrroles or spiropyrrolines with two exceptions. Lithium bromide/triethylamine induced cycloaddition of ethyl (benzylideneamino)acetate ( 7 ) with acyclic ct-oxoketene dithioacetals afforded either pyrrolidine, pyrrole or the corresponding 3-benzylideneamino-pyran-2-one derivatives depending on the reaction conditions and the structural variations in the a- oxoketene dithioacetals. Nitroketene dithioacetal also underwent anionic [1,3]cycloaddition with either 1 or 7 under described conditions to afford pyrrolidine or pyrrole derivatives. Probable mechanisms for the formation of various products are suggested.

Oxoketene dithioacetals as versatile synthons for alternative 1,3 to 1,11 carbonyl transpositions: A new polyene synthesis

A model strategy for 1,7 to 1,I1 carbonyI transpositions involving 1,2 addition of sodium borohydride or Grignard reagents to polyenyl oxoketene dithioacetals 8 obtained by condensation of bis(methylthio)polyenals 1- 3 with active methylene ketones, followed by borontrifluoride etherate catalyzed methanolysis of the resulting polyenyl carbinol acetals 9 to give 1,n transposed polyene esters 10 has been described.

Cyclocondensation of 2-lithiomethylthiazoles and 2-lithiomethylthiazoline with α-oxoketene dithioacetals: synthesis of substituted and annelated thiazolo- and dihydrothiazolo[3,2- a]pyridinium compounds

The oxoketene dithioacetals 1 undergo regioselective 1,2-addition with 2-lithiomethyl-4-methylthiazole ( 2a ) and 2-lithiomethylthiazoline (3) to afford the carbinol acetals 4 which on borontrifluoride etherate assisted cyclization yield the corresponding substituted and annelated 3-methyl-5- methylthiothiazolo[3,2-a.] pyridinium tetrafluoroborates ( 5a - g , 8a , b , 10 , 12 ) and the dihydro derivatives ( 23 - 25 ) respectively in good yields. The corresponding 2-methyl-5-phenylthiazole ( 16 ) however underwent both nuclear and side chain deprotonation and yielded a mixture of products under similar reaction conditions.

Completely regioselective reversals for an addition reaction of ambident sulphur nucleophiles to michael acceptors

Reacion of titanium enethiolates with α-unsaturated ketones leads selectively to 3-hydroxy 4-saturated alkanedithioates, arising from a 1,2-carbon-addition, whereas aluminum enethiolates give oxoketene dithioacetals, from exclusove 1,4-sulphur-addition.

Studies on diels-alder cycloadditions of vinylketene dithioacetals

The Diels-Alder cycloadditions of the acyclic and cyclic vinylketene dithloacetals 4 prepared from the corresponding oxoketene dithioacetals 2 either by 1,2-addition of methylmagnesium iodide and subsequent dehydration or by Wlttig reaction, were studied. Thus 4a-e and 4h-i underwent facile [4+2] cycloaddition with maleic anhydride followed by elimination of methylmercaptan and subsequent aromatization through dehydrogenation to give 5-aryl/methyl -3-nethylthiophthalic anhydrides ( 9a-e ), the corresponding tetrahydronaphthalene ( 13 ) and dihydrophenanthrene ( 14 ) derivatives in good yields. The vinylketene dithioacetals 4f and 4g derived from higher alkylketones, on the otherhand, underwent sequential [4+2] cycloadditions with two moles of maleic anhydride to afford bicyclic adducts 10a and 10b respectively,while the cycloadditions of dithioacetals 4a and 4f with dimethylacetylene dicarboxylate afforded the corresponding substituted phthalates 12a and 12b in good yields. The dienes 4a-i were found to be unreactive towards weaker dienophiles like acrylonitrile,ethylacrylate and methylvinyl ketones.

Darzen's reaction on oxoketene dithioacetals: A new versatile synthesis of substituted and annelated furan-2-carboxylates

Darzen's condensation of lithiobromoacetate with α-oxoketene dithioacetals affords the title furans 4 in moderate to good yields. A few of the 5-methylthio furan-2-carboxylates were desulphurized to yield 5-unsubstituted derivatives 5 in good yields. The reaction of α-cinnamoylketene dithioacetals 6 with lithiobromoacetate under identical conditions yielded the corresponding 5-methylthio-3-styryl furan-2-carboxylates 7 along with 3-(2-carbethoxy-3-aryl cycloprop-1-yl)-5-methylthio furan-2-carboxylates 8 which are shown to be formed by conjugate addition elimination of lithiobromoacetate on 7. The corresponding α-(5-aryl-2, 4-pentadienoyl)-( 9a-b ) and α-(7-aryl-2, 4, 6-heptatrienoyl)-( 11a-b ) ketene dithioacetals gave the corresponding 3-(4-aryl-1, 3-butadienyl)-( 10a-b ) and 3-(6-aryl-1, 3, 5-hexatrienyl)-( 12a-b ) 5-methylthio furan-2-carboxylates exclusively in good yields.

Novel cycloaromatization in reformatsky reaction on ∝-oxoketene dithioacetals: A regioselective synthesis of substituted ethyl 2-hydroxy-6-methylthiobenzoates

A novel cycloaromatization reaction leading to substituted ethyl 2-hydroxy-3-methylthiobenzoates 6 by condensation ∝-oxoketene dithioacetals 1 with excess of Reformatsky reagent 2 from ethyl bromoacetate through intermediate dienes 3 has been reported.

Cycloaromatization of ∝-oxoketene dithioacetals with 3-methyl-5-lithiomethylisoxazole: A new general approach for synthesis of substituted and annelated 1,2-benzisoxazoles

A new general method for the synthesis of substituted and annelated 1,2-benzisoxazoles has been developed by cycloaromatization of ∝-oxoketene dithioacetals with 3-methyl-5-lithiomethylisoxazole.

Aromatic annelation via ∝-oxoketene dithioacetals:synthesis of thioresorcinol dimethyl ethers

A novel aromatic annelation leading to fused thioresorcinol dimethylethers has been developed by reacting cyclic ∝-oxoketene dithioacetals with propargylmagnesium bromide followed by treatment of the resulting carbinolacetals with borontrifluoride etherate in methanol.

Polarized ketene dithioacetals. Part 42. Studies on the reactions of alkyl and aryl Grignard reagents with α-oxoketene dithioacetals

The oxoketene dithioacetals (2a–k) derived from a variety of cyclic and acyclic active methylene ketones undergo 1,2-addition with methylmagnesium iodide to give the alcohol acetals (3a–k) which, on subsequent boron trifluoride—ether catalysed methanolysis, yield methyl β-methyl-α,β-unsaturated esters (6a–k) in 51–70% overall yields. Also the alcohols (3a) and (3i–k) underwent partial hydrolysis in the presence of boron trifluoride–ether and water to yield β-methyl-α,β-unsaturated S-methyl esters (7a–d) in 41–60% yield. Under similar conditions however, the oxoketene dithioacetals (21–q) derived from higher homologues of acetophenone yielded the corresponding 2-alkyl-3-methylinden-1-ones (8a–f) in 50–62% overall yields. The reactions of cyclic oxoketene dithioacetals (2g), (2h), and (2j) with higher alkyl Grignard reagents afforded the alcohols (13a–f), formed by sequential 1,4 and 1,2 addition, which on subsequent methanolysis yielded the corresponding 1-(2-alkylcycloalk-1-enyl)alkan-1-ones (14a–f) in 48–58% overall yields. Similarly the phenylmagnesium bromide underwent sequential 1,4 and 1,2 addition to the oxoketene dithioacetals (2a–c), (2h) and (2j) to yield the alcohols (13g–k), which upon subsequent methanolysis yielded either 1,3,3-triarylprop-2-en-1-ones (14g–i) or phenyl (2-phenylcycloalk-1-enyl) ketones (14j–k) in 53–71% yield.