The Reaction of 4,5-Dichloro-1,2,3-dithiazolium Chloride with Sulfimides: A New Synthesis of N-Aryl-1,2,3-dithiazolimines

Abstract

N-Aryl-S,S-dimethylsulfimides 3 (Ar = 4-NO2C6H4), 4 (Ar = Ph) and 5 (Ar = 4-Tol) react with Appel salt 1 to give the corresponding N-aryl-(4-chloro-5H-1,2,3-dithiazolylidene)benzenamines 8 (Ar = 4-NO2C6H4), 9 (Ar = Ph) and 10 (Ar = 4-Tol) in 84, 94 and 87% yields, respectively. The reaction proceeds in the absence of base and a proposed reaction mechanism is given.

Ring transformations of 2-hydroxy-(4-chloro-5 H -1,2,3-dithiazol-5-ylideneamino)arenes

“…200 C for 1e5 min, gave the corresponding fused oxazoles 4aec in 60e85% yield, together with some S 8 (60e90%) ( Table 2, entries 4e6). Thermolysis of the (dithiazolylideneamino)pyridin-2-ol 5b also gave a small quantity of [1,2,3]dithiazolo [5,4-e]pyrido [2,3-b] [1,4]oxazine (6b) (1%) ( Table 2, entry 5). The reaction of the dithiazoles 5aec with NaH (1.1e2 equiv) in dry THF for 2 h heated at ca.…”

“…Thermolysis and base mediated ring transformations. The relative thermal stability of the 2-hydroxy(dithiazolylideneamino) arenes 5aec was indicated during their isolation and purification: both the (dithiazolylideneamino)phenol and pyridin-3-ol 5a and 5c, respectively, can be recrystallised as yellow cotton fibres from warm c-hexane, however, the (dithiazolylideneamino)pyridin-2-ol 5b was unstable and partly cyclised into oxazolo [5,4-b]pyridine-2-carbonitrile (4b) affording also traces of [1,2,3]dithiazolo [5,4-e] pyrido [2,3-b] [1,4]oxazine (6b). Purification of the (dithiazolylideneamino)pyridin-2-ol 5b was, therefore, carried out via precipitation in n-pentane from THF.…”

“…Similar 5,5-disubstituted 1,2,3-dithiazoles to the proposed spirocyclic intermediate 15 are known, such as the 5,5-difluoro-1,2,3-dithiazole 16a, 1 the dithiazole ketals 16b 33 and the spirocyclic lactams 17. 32b Rees also claimed that the oxazine 6a was not a precursor to the benzoxazole 4a since a pure sample was thermally stable at 200 C. 17a Nevertheless, ring contractions of 2H-benzo[b] [1,4]oxazin-2-ones 18a (X¼O) 34 and 2H-benzo[b] [1,4]oxazin-2-imines 18b (X¼NH) 35 into benzoxazoles 19a and 19b are known, and typically initiated by either thermolysis, 34i,j photolysis 34a,g or by nucleophiles such as hydroxide, 34bed,35 alcohols, 34f alkylamines 34e,f,k and hydrazines 34h,k (Scheme 7). The thermolysis of the dithiazoles 5 to give the oxazoles 4 leads to the formation of thiophilic by-products such as HCl and 'active' sulfur, which could affect the stability of any oxazine 6 that may form.…”

“…The latter cyclisation is analogous to the base (NaH or i-Pr 2 NEt in THF or K 2 CO 3 in MeCN) catalysed cyclisation of 2-(4-chloro-3H-1,2-dithiol-3-ylideneamino)phenols 7, prepared from 3,4,5-trichloro-1,2-dithiolium chloride (8) (Boberg salt) 26 and 2-aminophenols, to give 1,2-dithiolo [4,3-b] [1,4]benzoxazines 9, in moderate yields (39e45%) (Scheme 3). 27 Direct displacement of the dithiazoles C4 chlorine atom has proved to be difficult, 17a and the intramolecular cyclisation of the (dithiazolylideneamino)phenol 5a to afford the benzoxazine 6a is a very rare example of a cyclisation onto the dithiazole C4 position that maintains the integrity of the dithiazole ring.…”

“…Where the ortho substituent is a primary, secondary 19,24 or even a tertiary amine, 25 thermolysis affords the analogous imidazole-2-carbonitriles 3, and when the ortho substituent is a hydroxyl group the analogous benzo[d]oxazole-2-carbonitrile (4a) forms (Scheme 2). 17a,20 Surprisingly, in the latter case, treatment of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino) phenol (5a) with NaH in dry THF gave benzo[b] [1,2,3]dithiazolo [5,4-e] [1,4]oxazine (6a) (Scheme 2). 17a Scheme 1.…”