Carboxylic acid selenoamides

Selenoamides s. Carboxylic acid selenoamides Selenocarbonic... s. Triseleno-carbonic... 

Sodium hydrogen selenide Carboxylic acid selenoamides from iminochlorides... 

A mixture of thiobenzamide, 2-(cyclohex-l-enyl)cyclohexanone, and a little naphtha-lene-2-sulfonic acid in toluene refluxed for 24 h with azeotropic removal of water - cyclohexanespiro-2-(5-aza-4-phenyl-3-thiabicyclo[4.4.0]deca-1(6),4-diene). Y 63%. F.e. and 6-spiro-6Ff-l,3-selenazines from carboxylic acid selenoamides, also from carboxylic acid amides via treatment with Lawesson s reagent, s. C. Bochu et al., J. Org. Chem. 53, 4852-5 (1988). 

Carboxylic acid selenoamides. Dimethylformamide heated with 2.5 eqs. 2 M PhP(Se)Cl2 in xylene at 95-100° for 3 h - dimethylselenoformamide. Y 84%. Added NEt3 may improve the yield. F.e. incl. indolizine-3-selenaldehydes and l,2-dithiole-3-selenones s. J.P. Michael et al., J. Chem. Soc. Chem. Commun. 1988, 1494—6. 

Carboxylic acid selenoamides Isoselenocyanates Selenocyanates Selenoiminoesters... 

In most cases these C,N2 fragments are prepared by reaction of activated carboxylic acid derivatives (C, fragment), such as dithiocarboxylates 2, thioesters 3. nitriles 5, imidates 6, amidines 7, thioamides 8, selenoamides 9, selenoesters 11, orthocarboxylates 14, with hydrazine (N2 fragment) and are transformed to l,4-dihydro-l,2,4,5-tetrazines 17 without isolation. Therefore, these syntheses are treated as a (2 + 1 +2+1) fragment method. 

The chemistry of selenazoles is reviewed in a book <04MI777>. Addition of malonic dinitrile with phosphorus pentaselenide in aqueous ethanol affords selenomalonic diamide 282, which undergoes double cyclization with phenacyl bromide to furnish bis(selenazole) 283 <04S875>. 2-Acyl-l,3-selenazoles 287 are prepared in two steps from bromomethyl ketones 284 and selenoamides 285. A facile preparation of l,3-selenazole-5-carboxylic acids 289 is based on the cyclization of selenazadienes 288 with chloroacetyl chloride <048233>. 

---