Ylidene

The action of ammonia on N-(5-aryl-l,3-oxathioI-2-ylidene) tertiary iminium salts (7) affords linear intermediates that cyclize to 2-amino-4-phenylthiazoles (Scheme 7) (45). 

The linking methine cheiin includes an even number of methine groups (0,2,4). They are commonly named as derivatives of the ketomethylene ring, for example. 3-ethyl-5-(3-ethyl-4,5-diphenylthiazolin-2-ylidene)-rhodanine (5) and 4-[4- 3-methyl-4,5-diphenylthiazolin-2-ylidene)-2-butenylidene]-3-methyl-l-p-sulfophenyl-2-pvrazolin-5-one (6) (Scheme 4). 

Bivalent radicals derived from saturated unbranched alkanes by removal of two hydrogen atoms are named as follows (1) If both free bonds are on the same carbon atom, the ending -ane of the hydrocarbon is replaced with -ylidene. However, for the first member of the alkanes it is methylene... 

Aminophenyl)(4-imino-2,5-cyclohexadien-l-ylidene)methyl]-N-phenyl aniline, monohydrochloride [68966-31-4]... 

In a somewhat related reaction the fused lactone (142) furnishes the decahydropyrido[3,4- f]pyrimidine (143) during the reaction of a-(hydantoin-5-ylidene)-7-butyrolactone with ammonia in ethylene glycol at 200 °C (71KGS1280). 

Thiazol-3-ium, 3-ethyl-2-[A -(3 -ethyl-2 -thiazolylidene)-3-ylidene-1 -pro pen]-1 -yl-visible, 1, 345 (B-76MI11201) Thiazolo[2,3-a]isoquinolinium, anhydro-3-(4-bromophenyl)-2-mercapto-X-ray, 6, 669 (67JCS(B)1117)... 

Bi(l,2-dithiol-3-yl) ether reactions, 6, 801 Bi( l,2-dithiol-3-ylidene) pyrolysis, 6, 794 reactions... 

Divalent and trivalent radicals can be named analogously, using -diyl or -triyl with appropriate locants, or -ylidene or -ylidyne in the case of geminal di- and tri-radicals. 

Indigocarmine (2[l,3-dihydro-3-oxo-5-sulfo-2ff-indol-2-ylidene]-2,3-dihydro-3-oxo-lff-indole-5-sulfonic acid di-Na salt) [860-22-0] M 466.4, pK 2.8, pK2 12.3. Its... 

Alkylation of enamino ketones occurs on oxygen, as would be expected from the site of protonation. Thus 4-N-pyrrolidino-3-penten-2-one (47) gave N-(2-ethoxy-2-penten-4-ylidene)-pyrrolidinium iodide (48) on alkylation with ethyl iodide (22), and the enamino ketones derived from 5,5-... 

The enamino ketone (49) was reported to give no identifiable products on reaction with N,N-dimethyl carbamoyl chloride 63). However, reaction of (49) with N,N-diethyl carbamoyl chloride in refluxing chlorobenzene gave the N-(3-diethyl-amino-5,5-dimethylcyclohex-2-en-1 -ylidene)pyrrolidinium salt, isolated as the perchlorate. The latter must have been formed as outlined in Scheme I, involving initial O carbamoylation followed by an addition-elimination reaction to give 138 cation which can react with diethylamino anion by a further addition-elimination displacement to give the product 46). 

Concerning nomenclature, fulvalene 2 and its related systems 1 and 3-6 are the parent structures of this class of heterocyclic cross-conjugated compounds. Both ring systems are numbered as shown in formula 9 (1,4,5,8-tetraazafulva-lene) beginning at the heteroatoms. Alternatively, as in the case of heptafulva-lene 10 (3,3 -diazaheptafulvalene), the numbers 1-7 and l -7 can be used.Tlie use of the name of the parent heterocycle connected by an olefinic double bond is often favored for the nomenclature of electron-rich olefines, for example, bis[3-(2,6-diisopropylphenyl)-4,5-dimethylthiazol-2-ylidene] for compound 51a (97LAR365). Similarly, azafulvalenes of type 11 and 12 can be re-... 

Standard condensation reactions of formylfurazans with a variety of active methylene compounds have been performed to give reactive ylidene derivatives (99MI7) (Scheme 67). Yields ranging from 8% to 95% have been obtained. 

Ylidene-substituted furazans, which may be used in some cases without purification, are excellent building blocks for the construction of heteroaryl substituted derivatives. Simple variations in the substituents on the furazan ring, the active methylene compounds, and reagents can lead to a variety of products (99MI7) (Scheme 68). 

Imidazol-2-ylidene and its N,N -disubstituted derivatives as stable carbenes 99ACR913. 

Diisopropylphenyl)-4,5-dimethylthiazol-2-ylidene as a stable carbene 99ACR913. 

Several A -benzyl-thiazolidin-2-ylidene derivatives 155, 156 (95MI3) were oxidized to the corresponding 5,5-dioxides 157, 158 with 2,2 eq. of m-chloroper-benzoic acid. Although mild and controlled conditions were adopted, it was impossible to Isolate the intermediate 5-oxide which was probably very prone to oxidation to 157, 158. 

One method to transform imidazolium salts (00AGE3773) into carbene ligands, imidazol-2-ylidenes, is by deprotonation with sodium hydride or other suitable hydride in a mixture of THE and liquid ammonia (73JCS(D)514, 96CEJ1627, 98IC6412). 

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