Silver mediated direct C–H arylation of 3-bromoisothiazole-5-carbonitrile

Palladium catalyzed direct C–H arylation of 3-bromoisothiazole-5-carbonitrile with aryl/hetaryl iodides in the presence of AgF gave 13 4-aryl/hetaryl-3-bromoisothiazole-5-carbonitriles. The scope of this arylation was investigated and explanations for the limitations proposed. 3-Bromoisothiazole-5-carboxamide was isolated as a side-product, and its formation was attributed to Ag⁺-catalyzed hydration of the C-5 nitrile. The analogous phenylation of 3-chloroisothiazole-5-carbonitrile and 3-bromoisothiazole-4-carboxamide gave 3-chloro-4-phenylisothiazole-5-carbonitrile and 3-bromo-5-phenylisothiazole-4-carboxamide in 83 and 64% yields, respectively.     

Dithioester-enabled chemodivergent synthesis of acids,amides and isothiazoles via CC bond cleavage and CO/CN/CS bond formations under metal- and catalyst-free conditions

An operationally simple and user-friendly process to access privileged scaffolds such as acids, amides and isothiazoles has been devised employing β-ketodithioesters for the first time. Remarkably, the new protocol involves combination of CC bond cleavage and CO/CN/NS bond formations in one-pot. Aqueous ammonia led to the formation of skeletally distinct amide and isothiazole, whereas aqueous NaOH enabled the formation of aromatic acid near quantitative yield. This practical approach, which can dramatically streamline the synthesis of simple molecules, is highly chemoselective, cost-effective, amenable to gram scale, insensitive to moisture as well as bears high functional group compatibility.     

Isothiazoles. part X : New 3-substituted-2-arylpropenamidines by base catalyzed ring opening of 3-amino-4-arylisothiazole 1,1-dioxides

Starting from 5-unsubstituted or 5-alkyl-, aryl-, heteroarylsubstituted 3-diethylamino-4-arylisothiazole 1,1-dioxides by base induced ring opening 3-alkoxypropenamidines were synthesized in excellent yields in a mild and efficient way. When 5-bromo-3-diethylamino-4-arylisothiazole 1,1-dioxide was used as the reagent, 3,3-dialkoxy-propenamidines, a new class of unsaturated amidines, were obtained. By using Grignard reagents 3-substituted acrylamidines can be produced.     

Synthesis of Optically Active Isothiazole Derivatives from L-(α)-Amino Acids

Summary. Several enantiomerically pure 3,5-disubstituted isothiazol-5-ylideneamine hydrobromides were prepared by oxidation of chiral 3-amino-2,3-unsaturated thioamides. The starting thioamides derived from natural L-α-amino acids represent a novel group of synthetically useful chiral reactants.     

One-pot transformation of cyano oxiranes into furo[3,2-c]isothiazole derivatives

The one-pot reactions of 2-[amino(2-cyano-3-aryloxiran-2-yl)methylene]malononitriles with thiocyanate to afford 5-amino-3-arylfuro[3,2-c]isothiazole-6-carbonitriles in good yields.     

Microwave-induced generation and reactions of nitrile sulfides: an improved method for the synthesis of isothiazoles and 1,2,4-thiadiazoles

The 1,3-dipolar cycloaddition reactions of nitrile sulfides, generated by microwave-assisted decarboxylation of 1,3,4-oxathiazol-2-ones, have been investigated. By this approach ethyl 1,2,4-thiadiazole-5-carboxylates 3 were prepared in good yield by cycloaddition of the nitrile sulfides to ethyl cyanoformate. Similarly, reaction of benzonitrile sulfide with dimethyl acetylenedicarboxylate (DMAD) afforded dimethyl 3-phenylisothiazole-4,5-dicarboxylate (5). In contrast, o-hydroxybenzonitrile sulfide, generated from the corresponding oxathiazolone 2d, reacted with DMAD to give methyl 4-oxo-4H-[1]benzopyrano[4,3-c]isothiazole-3-carboxylate (8) in high yield. A ca. 1:1 mixture of ethyl 3-phenylisothiazole-4- and 5-carboxylates (6,7) was formed from benzonitrile sulfide and ethyl propiolate. The corresponding reaction with diethyl fumarate gave diethyl trans-4,5-dihydro-3-phenylisothiazole-4,5-dicarboylate (10). 3-Arylisothiazoles, unsubstituted at both the 4- and 5-positions, were prepared from the reaction of 5-aryl-1,3,4-oxathiazolones with norbornadiene by a pathway involving cycloaddition of the nitrile sulfide to the norbornadiene, followed by retro-Diels-Alder extrusion of cyclopentadiene from the resulting isothiazoline cycloadduct 12. In summary, the use of microwave irradiation, rather than conventional heating methods, allows nitrile sulfide generation and reactions to be carried out in shorter times, with easier work-up and, in some cases, in higher yields.