Arylmethylene compounds

Three isoxazolidinones are possible, the 3-, 4- and 5-isoxazolidinones, with 3-isoxazolidinones being the group containing the most members. Only one synthesis of 4-isoxazolidinones has been reported, although a number of 4-arylmethylene compounds exist. A number of isoxazolidine-3,5-diones have been synthesized. A review by Quilico with nine references appeared in 1962 (62HC(17)l,p. 7> and since then the number of references has slightly more than tripled. 

Annelation of cyclic imines with /3-dicarbonyl compounds <2004RCB393>, with cyclic /3-oxodithioesters <20010L229>, or with arylmethylene-/3-dinitriles <2002SC581> provides a one-pot route to quinolizidine systems, as exemplified in Equation 11 for the preparation of the 8-azasteroid 322. 

The 7i-donor behavior of 4-arylmethylene-2-phenyl-5(47/)-oxazolones 762 with the 7i-acceptor tetracyanoethylene has also been studied. The initially formed charge-transfer complex is converted via intermediate 763 to a new compound for which a 2-aryl-l-benzamido-3,3,4,4-tetracyanocyclobutanecarboxylic acid 764 has been proposed on the basis of the NMR spectral data (Scheme 7.233). Charge-transfer complexes of 2-aryl-4-arylidene-5(47/)-oxazolones with di- and trinitrobenzene as n acceptors have also been prepared. ... 

The Erlenmeyer reaction has also been used to prepare new 4-arylmethylene-2-[3-chlorobenzo[Z ]thien-2-yl]-5(4//)-oxazolones 800 from the appropriate A-acylgly-cine 799 and several aldehydes (Scheme 7.244). °° The pharmacological activity of these compounds as antibacterial and antiinflamatory agents has been studied. 

With aromatic and heteroaromatic aldehydes,193 4-oxo-6,7,8,9-tetra-hydro-4T/-pyrido[l,2-a]pyrimidines yielded the 9-arylmethylene derivatives,133,266 whereas with glyoxylic acid the 9-carboxymethylene derivative was formed.266,267 The primary addition product (237) could be isolated from the reaction mixture of ethyl 6-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidine-3-carboxylate and benzaldehyde. On dehydration the addition product (237) gave the 9-benzylidene compound.266 The 9-carboxymethylene derivatives may be transformed by catalytic hydrogenation to the 9-acetic acids, which can be esterified.266,267... 

Incorporation of the thiabutadiene moiety into a camphor framework resulted in the reaction with various dienophiles proceeding with complete Jt-facial selectivity and, in some instances, exo-selectivity. The stereochemistry of one product was confirmed by X-ray analysis. The (arylmethylene)thiocamphor compounds 429 were prepared by thionation of the corresponding ketones with Lawesson s reagent and exist as stable monomers (Equation 125) <1999TL8383>. 

Treatment of saturated azlactones with aromatic compounds under Friedel-Crafts conditions gives acylamino ketones in high yield (equation 46). 4-Benzyl-2-methyl-5(4H)-oxazolone undergoes an intramolecular reaction to yield an acetamidoindanone (equation 47). Friedel-Crafts reactions of 4-(arylmethylene)-5(4H)-oxazolones are complicated by the presence of an additional electrophilic centre (cf. 201) and may follow three courses. The unsaturated azlactone (189) adds benzene under the influence of aluminum chloride to form the saturated azlactone (207) in inert solvents (189) undergoes an intramolecular acylation to yield a mixture of the indenone (208) and the isoquinoline (209 Scheme 20). 

Arylacetylenes Aryl- and heteroarylacetylenes can be prepared in useful yields by condensation of aryl aldehydes with 1 to form 4-arylmethylene-5(4H)-isoxazoles (2). On flash pyrolysis (700-800°) these compounds lose CO2 and CHjCN with formation of acetylenes 3. 

A new route to triazolo[4,5-with sodium nitrite in acetic acid surprisingly gives oxazolo[5,4-[Pg.182]

Similarly, 2-arylmethylene-3,4-dihydronaphthalene-l(2//)-thione yielded the analogous spiro compounds in 62-88% yield. ... 

The essential step of this method is the electrocyclization of the azahexatriene system in 5-[(arylmethylene)amino]-6-[(./V,./V-dimethylamino)vinyl]-l, 3-dimethyluracils 5, which rearrange in situ following their formation from 5-(arylidene imino)-1,3,6-trimcthyluracils 4 and dimethylformamide dimethyl acetal. Aromatization then occurs by elimination of dimethyl-amine. The intermediate 6-[(W,Af-dimethylamino)vinyl] compounds 5 may be isolated in low yield.440 441... 

In a sodium ethoxide catalyzed condensation of 3,5-bis(arylmethylene)-4-piperidones 22 with ureas or thioureas, one of the exo-methylene functions is used to build up the pyrimidine part of a 8-methylene-l,4,5,6,7,8-hexahydropyrido[4,3-ethanolic solution of 1-methyl-3,5-bis(ferrocenylmethylene)-4-piperidone with an excess of thiourea in the presence of sodium ethoxide, the corresponding pyrido[4,3-r/]pyrimidine-2-thiol is obtained.512 The use of guanidine in this reaction affords the corresponding 2-amino compounds.513... 

A -Arylketenimine, 259 Arylmethylenemalondialdehyde, 180 2-Arylmethylene-l-tetralinthione, 217 Arylnitroso compound, 72-78 N-Arylpyrrole, 21-22, 73-74 A1-Aryls ulfiny limine. 259 Arylthienium salt, 233 4-Aryltriazolinedione, 159 N-Arylvinylketenimine, 259 Azabutadiene, 239-299... 

A number of pyrido[2,3-d]pyrimidines have been synthesised by reacting arylmethylene-acetoacetates with aminopyrimidines. The scope and limitations of the method were reviewed and it has be i deduced that the success of the reaction depends on the presence of the pyrimidine having a 6-amino group and a 2-oxo, thio, or amino group. The compounds were tested but were shown to have no calcium ion antagonist action or vasorelaxant potency [94T808S]. 

Reaction between arylmethylene acetoacetate 623 and aminoheterocycles 624 or 625 in DMF at 65 °C for 24-48 h led to the imidazo[l,5-u]pyrimidine derivatives 626 and benzo[4,5]imidazo[l,2-u]pyrimidine derivatives 627 in 74-80% and 68-78% yields, respectively. These compounds showed promising activity as calcium channel blockers (Scheme 122) (94MI1). When the reactions were exposed to MWI, the times were reduced to 1 min with comparable yields (95S389). 

Under similar conditions, the title compound is either used directly or presumed to be formed in situ from PdCl2 and CuBr2 to catalyze the rearrangement of 2-(arylmethylene)cyclopropyl-carbinols to afford (arylcyclobutenyl)carbinols with good to excellent regioisomeric ratios (eq 11). ... 

E)-Chalcones 4 were prepared via Claisen-Schmidt condensation of methyl ketones with different aromatic aldehydes. Cycloaddition reaction of 4 with thiourea yielded the eorresponding thioxypyrimidine 5 derivatives. Compounds 5 were condensed with chloroacetic acid to yield thiazolopyrimidine 6. Also thione 5 were also condensed, in one pot reaction, with chloroacetic acid and aromatic aldehyde to yield arylmethylene derivatives 7 which could also be prepared directly by condensation of 5 with aromatic aldehydes (Scheme 2) [14-20]. 

Acetyltetronic acid derivatives (94) are formed during base-catalysed rearrangement of 4-ethoxycarbonyl-3(2//)-furanones (93). 3-(Arylmethylene)-furandiones (95) can be obtained in fair yield froni tetronic acid itself (for which an improved preparation has been found) by condensation with aromatic aldehydes (three equivalents ) in the presence of concentrated hydrochloric acid. Butyrolactones are transformed into their 2-keto analogues upon dye-sensitized photo-oxygenation of their readily available 2-dimethylaminomethylene derivatives, the overall yield for the two steps, with model compounds, being about 60%. °"... 

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