Thiazoline system

The sulfoxide (35) of the isomeric 2-ethyl-3-imino-l,2-benziso-thiazoline system (31) is obtained by reaction of 31 with chlorine water, and dechlorination of the intermediate A -chloro compound (34) with hydrogen chloride in carbon tetrachloride.26 Other sulfoxides have been reviewed by Bambas.1... 

In this synthesis the formation of the thiazoline system 31 32 is carried out at 0 C in ether. Thus a good yield and a high degree of stereoselectivity (> 4 1) is achieved. 

P,N-CHELATING LIGANDS BASED ON OXAZOLINE/THIAZOLINE SYSTEM... 

Amino-4-phenylthiazole when heated with Raney Ni is reported to yield acetophenone (469). In the course of a general study on reductive cleavage in heterocyclic systems Hoff et al. studied the reaction of 2-amino-4-methylthiazole with Na in liquid ammonia. Two equivalents of Na are necessary to obtain a mixture of 4-methyl-3-thiazoline (240) and... 

Acrylonitrile reacts with the sodium salt of 4.5-dimethvl-A-4-thiazoline-2-thione (73J (R4 = R5 = Me) to yield 3-(2-cyanoethyl)-4.5-dimethyl-A-4-thiazoline-2-thione (74) (R4 = R, = Me) (Scheme 35 (160). Humphlett s studies of this reaction showed that the size of the R4 substituent is a determinant factor for the S versus N ratio (161. 162). If R4 == H, 100% of the N-substituted product (74) is obtained this drops to 50% when R4 = methyl, and only the S-substituted product (75) is obtained when R4 = phenyl. The same trend is observed with various CH2 = CH-X (X = C00CH3. COCH3) reagents (149). The S/N ratio also depends on the electrophilic center for CH2 = CH-X systems thus S-reaction occurs predominantly with acrylonitrile, whereas N-substitution predominates with methvlvinvlketone (149). 

Tautomerism of the A-2-thiazoline-5-thiones has not been investigated intensively. A recent report shows that 2-phenylthiazo e-5-thiols exist in the thiol form in both polar and nonpolar solvents (563). This behavior is in contrast with that of corresponding thiazolones. Addition reactions involve only the exocyclic sulfur atom, and thiazole-5-thiols behave as typical heteroaromatic thiols towards unsaturated systems, giving sulfides (1533) (Scheme 80) (563),... 

Hansa Yellows, 1, 334 5, 299 Hantzsch synthesis, 2, 87-88 1,4-dihydropyridine, 2, 482 thiazoles, 6, 294-299 A -thiazolines, 6, 314 Hantzsch-Widman names parent names, 1, 35 stem suffixes, 1, 12 Hantzsch-Widman system nomenclature, 1, 11-12 Hardeners in photography... 

The 2,2/-bi-2/-thiazolines 16 17 18 (Dq(Ni2+) values 1160, 1120 and 1160 cm-1, respectively) are related to the bithiazoles, and the perchlorate salts of the [Fe N6]2+ derivatives of all three systems are low spin at room temperature but their behaviour above room temperature has not been reported. The low spin configuration for [Fe 173](C104)2 in particular appears inconsistent with the behaviour of related systems containing substituents adjacent to the donor atoms, and with its relatively low Dq(Ni2+) value. Nelson and co-workers have pointed out that the steric effect here is not so pronounced because the methyl substituents are not coplanar with the diimine group [21]. 

Reactions of Acetoin and Aldehydes with Ammonium Sulfide. This reaction leads to the various substituted oxazolines, thiazolin-es, and Imidazolines. Additional heterocyclic systems identified in this reaction include thiophenes and pyrazines. All these products are important aroma compounds in the food industry. 

HC104-CH2C12) with vigorous stirring [Eq. (121)]. The direction of the current was changed every 30 sec by means of a commutator. The labile thiazoline and /J-lactam ring systems were not affected by HC104 in the two-phase system.343... 

A variety of heterocyclic systems have been used for forming merocyanines. The more usual nitrogen-containing heterocycles involved include benzimidazole, quinoline, ben-zothiazole, benzoselenazole, thiazole, thiazoline and indolenine. Among the more useful carbonyl-containing heterocycles are derivatives of 2-pyrazolin-5-one, 2-thiobarbituric acid, rhodanine and hydantoin. 

Reduction of the parent systems is of little importance as reduced forms of 1,4-oxazines and -thiazines are readily available by other means moreover, hydrogenation of thiazines may effect cleavage and ring contraction to thiazolines rather than straightforward addition to a double bond as was once supposed (Scheme 39) (68G17). 

The generation of four-membered ring systems can be accomplished by a cycloaddition process under photochemical conditions or with special substrates under thermal conditions. Iron-vinylidene complexes belong to such a class of special substrates where a thermal [2 + 2]-cycloaddition is possible. If imines are used, a hetero-[2 + 2]-cycloaddition with an iron-vinylidene complex leads to an iron-carbene complex attached to an azetidine ring system, as reported by Barrett and coworkers (Scheme 9.20) [46, 47]. The oxidation of these iron-carbene complexes leads to [3-lactams 27. Interestingly, the application of 2-thiazolines generates penam... 

Preparation of Standards and Model System Reaction Mixtures N -Nitroso-l,3-thiazolidine was prepared by direct nitrosa-tion of 1,3-thiazolidine and also from reaction of cysteamine/for-maldehyde/nitrite. Details for the experimental procedures involved in the preparation and work up of these standards and mixtures will be presented elsewhere (10). Quantitative determination of 1,3-thiazolidine and IJ-nitroso-1,3-thiazoline were obtained for seven reaction mixtures (10) ... 

An alternative electrochemical route to the thiazoline-azetidinone 36 also has been developed. Carboxylic acid 39 prepared from penicillin G can be converted to 36 via 40 by electrochemical decarboxylative acetoxylation followed by hydrolysis (Scheme 2-13)The electrolysis of 39 in an AcOH/DME—AcONa—(C) system at 0 °C... 

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