4.5- Dichloro-l ,2,3-dithiazolium chloride

Scheme 8.11 Reagents and conditions (for time and yields of steps ii, iii, vi, and vii see Tab. 8.3). (i) 4,5-dichloro-l,2,3-dithiazolium chloride, pyridine, rt, 10 h (ii) NaH, EtOH,...

Aminotetrazole reacts with 4,5-dichloro-l,2,3-dithiazolium chloride 166 to afford the bis(imino-l,2,3-dithiazole) 167 (20%) which in warm DMSO or DMF converts into the 1,2,3-clithiazolimine 168 (25%) (Scheme 16) <2002J(P1)1535>. 

A possible synthesis of the extensively studied 4,5-dichloro-l,2,3-dithiazolium chloride (Appel salt) analogs (see next section) was found in the reaction of acetophenone oxime and its 4-nitro derivative with S2CI2 (1994H1827, 1997BSB605 Scheme 73). 

In the post-1980 period more attention has been paid to heteropentalene structures. An abundance of new chemistry has been revealed for 4,5-dichloro-l,2,3-dithiazolium chloride ( Appel s salt ),... 

In the condensations of o-aminohenzyl alcohol 376 or anthranilic acid 401 with 4,5-dichloro-l,2,3-dithiazolium chloride (Appel s salt) 402, imino-l,2,3-dithiazoles 403 were formed. Heating of the imino alcohol 403 (X = H2) in THE in the presence of NaH afforded an 11 1 mixture of 3,1-benzoxazine 404 and 3,1-benzothiazine 405 in moderate yield. Thermal cyclization of imino acid 403 (X = 0) resulted nearly quantitatively in formation of 3,1-henzoxazin-4-one 406 (Scheme 76) <1995CC1419, 1995J(P 1)2097, 1997SL704>. 

While studying the chemistry of 4,5-dichloro-l,2,3-dithiazolium chloride (Appel s salt) and its derivatives, Besson reported the synthesis of various benzothiazoles from N-arylimino-l,2,3-dithiazoles, which could be synthesised from commercially available aromatic amines28. In this work, the authors explored a variety of strategies to construct the benzothiazole ring and demonstrated that in all cases the focused microwave methodologies were more productive and under well-defined conditions provided convenient methods for scale-up (Scheme 3.17)28. Comparisons were also made between reactions performed under solvent-free conditions and in the presence of solvent29. It is noteworthy that there is no general rule and some reactions performed in the presence of solvent may sometimes be more convenient than the same dry media reaction. 

The X-ray analysis of 4,5-dichloro-l,2,3-dithiazolium chloride 20, often referred to as the Appel salt, reveals a pattern of bonding within the dithiazole ring that indicates delocalization that extends around the ring from one sulfur atom... 

Reduction of the reaction time was achieved by the use of microwave dielectric heating in synthesis of 2-cyanobenzothiazoles from anilines and 4,5-dichloro-l,2,3-dithiazolium chloride [84,85]. Mn(OAc)3 promoted the radical-mediated cyclization of aryl- and benzoyl-thioformanilides. The re-... 

A -Monosubstituted 1,2-diaminobenzenes 1497 (R = Me, Ph, PhCH2, and 3,4-Me2C6H3CH2) react with 4,5-dichloro-l,2,3-dithiazolium chloride 1498 in dichloromethane at room temperature to give the corresponding imines 1499 which undergo thermolysis to form 2-cyanobenzimidazoles 1500 in fair to good yields (Scheme 387) <1998T9639>. 

Cyanothiazoles 33 are prepared from A -vinyl-l,2,3-dithiazolimines 31, obtained from the reaction of 4,5-dichloro-l,2,3-dithiazolium chloride 29 with aziridines 28 <05H(65)1601>. Thermolysis of imines 31 brings about cyclization to give sulfur, hydrogen chloride and 2-cyanothiazoles 33, possibly by an electrocyclization and fragmentation process. Reaction of allenyl isothiocyanate 34 with a variety of nucleophiles (NuH) leads to... 

One of the most studied microwave-assisted formations of the benzothiazole ring is initiated by an addition-elimination reaction. Treatment of aniline derivatives with 4,5-dichloro-l,2,3-dithiazolium chloride (commonly called Appel s salt) gave 4-chloro-5]-f-l,2,3-iminodithiazoles (47) which are very versatile intermediates in the synthesis of a variety of heterocycles (Scheme 9.15). Besson and coworkers... 

Condensation of 4,5-dichloro-l, 2,3-dithiazolium chloride 23 (Appel s salt) with various ort/zo-halogenated anilines and aminopyridines 22 gives the... 

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