Benzothiazolyl group

The nature of the carboxamide aryl substituent has a dramatic effect on the pharmacokinetic properties, with the 2-benzothiazolyl group leading to a longer half-life compared to a phenyl group. 

The carboxy group of levofloxacin was converted into 6-(2-benzothiazolyl) group with 2-aminophenol in PPA at 170-250 °C for 4h in 51% yield (09JMC5649). 

The benzothiazolyl group (BT) can play several roles in one, it enables a more or less strongly pronounced complexation that influences the selectivity on the other hard, it can also undergo nucleophilic substitution at the carbon attached to the sulfonyl group, which then becomes a leaving group. Other (hetero)cyclic substituents can assume these roles, and offer somewhat different selectivity ... 

As regards solvent effects, it seems likely that in nonpolar solvents, rotation around the central bond in the Smiles rearrangement product will be retarded by intramolecular bounding of the lithium cation by SO2 and the benzothiazolyl group. 

Of the urea derivatives containing the benzothiazolyl group as substituent two compounds are used in agriculture benzthiazuron, I-(benzothiazol-2-yl)-3-methylurea (43) (Hack et ai, 1966) and methabenzthiazuron, l-(benzothiazol-2-yl)-3,3-dimethylurea (44) (Searle, 1956 Hack et al, 1967 Hack, 1968). The former is selective in sugar beet and spinach, the latter in cereals, pea, bean and other crops. 

Sulfidation of the brass surface is not due to its interaction with elemental sulfur, but it is the result of the interaction between the brass surface and accelerator-sulfur reaction products, which can be represented by the general structure, Ac-S -Ac and Ac-Sy-H, where Ac is an accelerator-derived moiety (e.g., benzothiazolyl group). The value of the subscript, y, increases with the ratio of the concentration of sulfur to the concentration of accelerator used in the curing system. Generally, high sulfur levels and high ratios of sulfur concentration to accelerator concentration favor good rubber-to-brass adhesion. 

TTie chemistry of the accelerated vulcanization of BR, SBR, and EPDM appears to have much in common with the vulcanization of natural rubber Before the formation of crosshnks, the rubber is first sulfurated by accelerator-derived polysulfides (Ac-S -Ac) to give macromolecular, polysul-fidic intermediates (rubber-Sx-Ac). However, whereas in the case of MBTS-or benzothiazolesulfenamide-accelerated sulfur vulcanization of natural rubber, MBT is given off during the formation of rubber-Sx-BT from the attack of rubber by BT-S -BT, in the case of BR and SBR, MBT is not eliminated and remains unextractable presumably because it becomes bound as the macromolecular thioether rubber-S-BT. (BT is a 2-benzothiazolyl group.) As in the case of natural rubber, the average length of a crosslink (its sulfidic rank, the value of x in the crosslink, rubber-Sx-rubber) increases with the ratio of sulfur concentration to accelerator concentration (S/Ac) used in the... 

The importance of coordination in dictating the stereo- and regioselectivity is further demonstrated by the reactions of a,/3-enoates /-substituted by a 5-benzothiazolyl group with organocopper reagents to give, in a anti-Michael fashion, a-alkylated- 8,/-enoates (eq 6). 

Spectral properties and dissociation constants of a series of phenols carrying in their ortho- or para-position a heterocyclic substituent (including the benzothiazolyl group) have been determined. The linear relation of dissociation constants with Hammett o-p constants was used to calculate substitution constants for the heterocyclic residues. Owing to their electron-withdrawing effect, the hetero-substituents invariably enhance the acidity of the phenolic hydroxy-group. 

Both benzothiazolyl and berizolriazoly] units have been employed as heteroaromatic anion-stabilizing groups for metalated epoxides (Scheme 5.47) [71]. The successful use of a simple alkyl bromide as electrophile with 200 is notable. 

In a related series of 1,2,4-trisubstituted anthraquinone compounds, the effectiveness of various polar and nonpolar substituents to improve on the low heat fastness of 2-amino-1,4-dihydroxyanthraquinone (3.184 R = H) was examined (Table 3.50). Short-chain alkyl groups (methyl, ethyl) and even the pyranylmethyl ether are relatively ineffective but hydroxyalkyl, cyclohexyl, benzyl and morpholinylethyl groups show moderate increases. Further improvement is given by phenyl, pyridylmethyl and morpholinylpropyl. Outstandingly effective, however, are the benzothiazolyl, dodecylphenyl and fluoro-methylphenyl groupings. 

Other examples of (trialkylsilyl)azaheterocyclic systems where direct reaction has resulted in ipso substitution of the silyl group include 2-pyridyl [69JHC433 72JOM(38)29 76JOM(104)153], 2-benzothiazolyl (71JHC257 73CB594 85TL5477), l-methyl-2-imidazolyl and 1-methyl-... 

The best evidence for the photolytic decomposition of mercaptans and disulfides into free radicals involves photoinitiation of polymerization of olefins. Thus, photolysis of disulfides initiates the copolymerization of butadiene and styrene,154 as well as the polymerization of styrene207 and of acrylonitrile.19 Thiophenol and other thiols promote polymerization upon ultraviolet irradiation.19 Furthermore, the exchange of RS-groups between disulfides and thiols is greatly accelerated by light. Representative examples are benzothiazolyl disulfide and 2-mercapto-thiazole,90 tolyl disulfide and p-thiocresol, and benzyl disulfide and benzylmercaptan.91 The reaction probably has a free radical mechanism. Similar exchange reactions have been observed of RS-groups of pairs of disulfides have been observed.19... 

The widely used phenylureas have their heterocyclic counterparts, particularly amongst the 1,3,4-thiadiazoles. They are persistent total herbicides and important examples are tebuthiuron (11) (69GEP1912543) and thiazafluron (12) (69GEP1816696). Benzothiazolyl ureas such as methabenzthiazuron (13) (67BRP1085430) and benzthiazuron (60JIC621), which lacks the 1-methyl group, are also herbicidal. 

Heterocyclically substituted acetic acids (e g., benzothiazolyl-, benzimidazo-lyl- [34], and pyrimidylacetic acids [35]) are also suitable as coupling components for preparing cationic hydrazone dyes. In these compounds the methyl group in the 2-position is additionally activated. The carboxyl group is split off after coupling and the azo base is methylated. 

The behavior of bis(heteroaryl)methanes in which the heterocycle was an electron-withdrawing group was similar to that typically exhibited by active methylene compounds. Bis(2-benzothiazolyl)methane and bis(2-(5-ethoxycarbonyl-4-methyl)thiazolyl)methane readily underwent azo-coupling with benzenediazonium chloride, nitrosation with nitrous acid and condensation with aromatic aldehydes under mildly basis conditions, such as in the Knoevenagel procedure. [94G301]... 

Chromoionophores of crown 4 and spherand cyclophane-type 5 with 2,4-dinitrophenylazophenol groups as a chromophore were also designed [7 a]. They show marked color changes from yellow into blue on complexation with cations in ethanol and chloroform solutions. This chapter describes selective complexation and coloration of azophenol hosts or fluorescent emission of benzothiazolyl crowns with alkaline metal ions and alkyl amines. 

Like the benzothiazolyl (BT) group, other heterocyclic groups such as pyridyl (py), phenyltetrazolyl (PT) and fert-butyltetrazolyl (TBT) can also assume these roles and offer somewhat different selectivity. 

The positive values of a, constants for heteroaromatic groups reported by Bystrov et al. (68ZOB1001) decrease in the sequence 2-benzoxazolyl > 2-benzothiazolyl > jV-phenyl-2-benzimidazolyl > Af-methyl-2-benzimidazolyl. The values of the constants decrease in the same sequence. This indicates the electron-releasing ability of condensed 2-hetaryls to increase in the above sequence, which conforms with their properties. 

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