1,2,4]-triazolo[3,4-b][1,3,4]thiadiazole, tetramethylthiuram disulfide.Aryl isothiocyanates are widely used in preparative organic synthesis, but their accessibility is limited primarily by the cost and risk of the thiophosgene method [1]. So it is important to look for alternative methods for synthesis of aryl isothiocyanates using a process that is accessible, low cost, and safe.In reactions with aliphatic and aromatic amines, tetramethylthiuram disulfide (TMTD) forms N (1) -alkyl(aryl)-N,N-dimethylthioureas [2][3][4][5]. The latter, when treated with excess acetic anhydride, acetyl chloride, sulfuric or hydrochloric acid, undergo degradation to form the corresponding isothiocyanates [5].We have developed a one-pot method for obtaining the aryl isothiocyanates 3a-e from the corresponding aromatic amines 1a-e and 80% wettable TMTD powder. Preliminary isolation and purification of the active substance from off-grade TMTD fungicide does not result in a significant increase in the yield of the final reaction product, so thiocarbamoylation of the aromatic amines was carried out by boiling equimolar amounts of the reagents in ethanol together with the filler. The thioureas 2a-g obtained in this case, when boiled with a three-fold excess of concentrated hydrochloric acid, form the corresponding aryl isothiocyanates 3 (Scheme 1).We know [6] that when substituted o-aminophenols are boiled with TMTD, the reaction does not stop in the step of formation of the corresponding thiourea but rather further cleavage of the N,N-dimethylamino group occurs, followed by cyclization to form substituted 2-mercaptobenzoxazoles. When TMTD is reacted with 5-(2-aminophenyl)-1,3,4-oxadiazole-2-thiol, after initial formation of thiourea, the adduct undergoes a series of sequential rearrangements with formation of 2-mercapto-1,3,4-thiadiazole[2,3-b]quinazolin-5-one [7]. Based on __________________________________________________________________________________________
