1.2- Dihydro-5/7-thiazolo

The only known example of thiazolo-l,5-benzothiazepines is 1,2-dihydro-5//-thiazolo[2,3-c/][l,5]benzothiazepin-5-one (83), obtained in very low yield (3%) by cyclization of 4-thione derivative 82 with 1,2-dibromoethane in ethanol containing sodium acetate (Scheme 24) (80CB2314). 

Sulfur atom as internal nucleophile. In this area, it has been shown that the reaction of 8-bromo-l,3-dimethyl-7-(2,3-epithiopropyl)xanthine 147 with a range of aliphatic and aromatic amines generates efficiently 2-amino-substituted 2,3-dihydro-thiazolo[2,3-/]xanthine derivatives 148. The process involves a sequential amine-induced thiirane ring opening followed by thiolate z/MYi-substitution of chlorine atom (Equation 66) <1994PCJ647>. 

The iodocyclization of 2-methallylmercapto benzimidazole 247 proceeded in a regioselective manner by treatment with iodine and aqueous KOH in chloroform to give the dihydro-thiazolo[3,2- ]benzimidazole 248 (Equation 108) <1999RJO730>. 

With ketones. The 17/-imidazole-2(377)-thione 378 and 2-mercaptobenzoimidazole 380 reacted separately with cycloheptanone to form the tetrahydro-imidazo[2,l- ]thiazole 379 and the dihydro-thiazolo[3,2-tf]benzimidazole 381, respectively (Equations 170 and 171) <2000JHC943, 2001RJ0564>. 

With S-vinylsulfilimines. A novel synthesis of the dihydro-thiazolo [3,2- ]benzimidazole 414 was achieved by the ring closure of 2-mercaptobenzoimidazole 412 using d -ethenylsulfilimine 413 and basic conditions (Equation 188)... 

Dimethoxy-3-methyl-l-(4-nitrophenyl)-iV-(5, 6 -dihydrothiazolo[3,2-b][l,2,4]triazol-2 -yl)isoquinolinmm bromide 45 is also prepared by reacting 4,5-dimethoxy-2-(4-nitrobenzoyl)phenylacetone 219 with 2-amino-5,6-dihydro-thiazolo[3,2- ][ 1,2,4]triazole 42 <2003JHC821, 2003JHC1041> (Equation 23). 

The reaction of 2,3-diaminoquinazolin-4-one 404 with aryl aldehydes and thioglycolic acid gives 2-substituted 1,3-dihydro-thiazolo[3, 4 2,3][l,2,4]triazolo[5,l-A]quinazolin-5-ones 405 (Equation 79) <2004MI10>. 

Similarly, 3-(5-mercapto-l,2,4-triazol-3-yl)-7-methyl-l,4-dihydro-4-oxo-l,8-naphthyridines 432, after reaction with substituted benzaldehydes, chloroacetic acid in the presence of the mixture of acetic anhydride and acetic acid, gives the corresponding 3-(6-arylidene-5-oxo-5,6-dihydro-thiazolo[3,2- ]-l,2,4-triazol-2-yl)-7-methyl-l,4-dihydro4-oxo-1,8-naphthyridines 433 (Equation 92) <2002EJC323>. 

Several groups have reported reactions giving thiazoloquinazoline compounds, probably the most interesting of which is the cyclization-ring expansion of the aziridine thiourea derivative 225 to the dihydro-thiazolo[2,3-6]quinazoline 226 in hydrochloric acid of Howard and Klein.395 Other preparations of this ring system involve the treatment of l-(2-carbethoxyphenyl)-2-thioureas with a-chloro 396-398 or a-bromo396,397 ketones or with vicinal dibromides.398 Tetrahydro salt... 

Cyclization of the 4-phenylhydrazono derivatives of 2-thiazolidinone with formaldehyde or aromatic aldehydes gives 2-phenyl-2,3-dihydro-thiazolo[4,3-c]l,2,4-triazol-5-ones (131) [Eq. (39)] subsequent condensation with aldehydes affords the corresponding 7-arylidene derivatives.171... 

A convenient synthesis of thiazolo-fused 2-pyridones 41 has been developed <07JOC4917>. Thus, A2-thiazolines 39 undergo acyl ketene imine cyclocondensation with Meldrum s acid derivatives 38 to give the dihydro thiazolo-fused 2-pyridones 40, which transform to 41 via bromination-elimination process. Pyridones 41 are converted to the 2-substituted analogs 43 and the saturated products 42 by Heck coupling and conjugate addition, respectively. 

Dihydro--bromid reagiert mit N-Nukleophilen untcr Offnung des 4,5-Dihydro-l,3-thiazol-Ringes zu 2-Imino-2,3-dihydro-l,3-benzothiazo-len1011 ... 

The third access was based on the reaction of 1,2-dibromoethane with 2-mercapto-purin-9-one or 2-mercaptoadenine and their derivatives. Preparation of compound 83 from potassium or sodium 2-mercaptoinosine (84) with an excess of 1,2-dibromoethane in water exemplified the first reaction according to Scheme 22. The annulation site of thiazole to purine moieties was proven by desulfuration with Raney-nickel (after previous cleavage of the saccharide grouping) by the appearance of 1-ethylhypoxanthine (74CPB342). An example for the second reaction was the cyclization of 2-mercaptoadenine with an excess of dibromoethane giving a mixture of 3,6,7,9-tetrahydro-9-iminothiazolo[3,2-u]purine (85) and isomeric 4-amino-7,8-dihydro-thiazolo[2,3-7>]purine (86). Both isomers were separated by their much different insolubility in chloroform (80JHC583) (Scheme 23). 

Aromatic aldehydes undergo aldol condensation with the 6-methylene group of 5,6-dihydro-thiazolo[2,3-c][l,2,4]triazol-5-ones (100) to give the 6-arylidene derivatives (101) (Scheme 4) <89JIC832, 90JIC226, 90JIC409). 

The treatment of the 2-(4-chloromethylthiazol-2-yl)hydrazone of a heteroaromatic aldehyde (196) (formed as an intermediate in the reaction of some thiosemicarbazones with 1,3-dichloroacetone) with acetic anhydride gives rise to 3-hetaryl-substituted 2-acetyl-5-chloromethyl-2,3-dihydro-thiazolo[2,3-c][ 1,2,4]triazoles (197) (Scheme 17) <92JIC596>. 

Thiazolo-[2,3-c]- and -[3,2-6]-[l,2,4]thiadiazoles [CaNgS-CaNS].—Condensations of a-amino-N-heterocycles with chlorocarbonylsulphenyl chloride in the presence of an organic tertiary base can give rise either to a 2,3- or to a 3,4-fused [1,2,4]-thiadiazolone. Thus, 2-aminothiazole yields 2JT-thiazolo[3,2-b][l,2,4]thiadiazol-2-one in THF (see Vol. 3, p. 684). The isomeric 2,3-fused system is formed in ethanol-free chloroform. 2-Amino-A -thiazoline similarly yields 5,6-dihydro-thiazolo[2,3-c][l,2,4]thiadiazol-3-one, the structure of which has been confirmed by X-TQ.y analysis. ... 

Cyclization of 6-amino-8-(2-hydroxyethylthio)purine with polyphosphoric acid gives a mixture of 4-amino-6,7-dihydrothiazolo[2,3-/]- and 4-amino-7,8-dihydro-thiazolo[3,2-e]-purines. The 8-propargylthio-derivatives are cyclized on treatment with hydrogen halides to give the corresponding thiazolo[3,2-e]-purines. ... 

Reaction of 2-aminothiazole with ethyl acrylate yields 5.6-dihydro-7H-thiazolo[3,2a]pyrimidin-7-one (116) (Scheme 78) (169). 

Refluxing, 5.6-dihydro-7H-thiazolo[3,2-a]pyrimidine-7-one (370j with isopropylamine led to 2-imino-3-[2-(isopropylaminocarbonyl)ethyl]-thiazoline (371) (108). Similarly. tetrahydrobenzothiazolo[3,2-fl][2.3-f>]-quinazoline is opened by potassium hydroxide, yielding 373 (Scheme 214)... 

Thiazolo[3,2-a]pyridinium, 6-amino-2,3-dihydro- H NMR, 6, 675 (78ACS(B)70) Thiazolo[3,2-a]pyridinium, anhydro-7-bromo-3a-carboxy-2,3-dihydro-8-hydroxy-2ft5-dimethyl-1 or-0X0-... 

Thiazolo[3,2-a]py ridinium, anhy dro-3 -carboxy-2,3 -dihydro-8-hydroxy-pK, 6, 682 (72ACS1847)... 

Thiazolo[3,2-a]pyrimidinium, anhydro-8-ethyl-2,3-dihydro-5,7-dioxo-IR, 6. 681 (73JHC487)... 

---