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Heterocyclic derivatives alkylation

The mesomeric effect of the C=S linkage is very pronounced and is responsible for the facile quaternization of heterocyclic N-alkylated thiones (159) this effect is operative even when such a shift does not increase the aromaticity of the ring. Thione derivatives of pyridazine, benzothiazole, quinazoline, 1,3-thiazine, triazole,and isoindole are examples of compounds which readily form quaternary salts. [Pg.51]

A recent paper from Katritsky summarises all the preparations of achiral dissymmetrical thioureas and proposes a new one, based on l-(alkyl/arylthio-carbamoyl)benzotriazoles, which act as masked isothiocyanates. As described in the previous section, other N-heterocyclic derivatives can be used instead... [Pg.234]

The reaction of dimedone with 3-alkyl-5-ercapto-1,2,4-triazoles 315 in the presence of NBS gives intermediates, which after reaction with a solution of aqueous sodium carbonate afford 2-alkyl-5a-hydroxy-6,6-dimethyl-8-oxo-5a, 6,7,8,8a-hexahydro[l,2,4]triazolo[3,2-3]benzothiazoles 49. Finally, reaction with PPA provides the dehydrated heterocyclic derivatives 316 (Scheme 30) <1999IJH127>. [Pg.257]

The range of organic compounds which have been subject to the Simons process is wide and includes aliphatic and aromatic hydrocarbons, halocarbons, ethers, aliphatic and aromatic amines, heterocyclics, thiols, alkyl sulphonic and carboxylic acids, and their derivatives, among others. [Pg.214]

To expand the diversity of their libraries Brill et al.16 also modified various heterocycles by alkylation, acylation, or metal-mediated coupling reaction prior to resin capture. A remaining chloro substituent was still available for nucleophilic displacement or a palladium-mediated coupling reaction with anilines, phenols, and boronic acids on solid phase [see Fig. 10 for the preparation of purine derivative (62)]. [Pg.439]

Alkylation of amino acids has also been achieved by first foiming heterocyclic derivatives. For example, the oxazolidinone fitrni CBZ-phoiylalanine and foimalddtyde reacts with potassium hexar methyldisilazide followed 1 allyl bnxnide to give the expected product in 76% yield.Chiral tetrahy-dro-l,4-oxazin-2-oiies have be used in a similar manna to give amino acids with a degree of diastereoselectivity. ... [Pg.230]

Gonzales Trigo. G.. Galvez Ruano, E., and Mcnendez Aguirre. C.. Spiro heterocyclic derivatives. XV. Some N-methyl-N -alkyl (or aralkyl) -3.7-diazabicyelo 0. 3.3.1 nonan-9-ones and. some, spiro-5 -hydanioin derivatives of 3,7-diazabicyclo(3.3.l Inonanes. An. Quim.. 75, 894, 1979 Chem Ahstr., 93. 26411, 1980. [Pg.233]

Glycosyl isothiocyanates have also been allowed to react with unprotected 2-amino-2-deoxyaldoses and 1-amino-1-deoxy-2-ketoses.68 This reaction leads to the formation of heterocyclic derivatives resulting from cy-clization involving the carbonyl group of the amino sugar moiety following the mechanistic pathway already discussed for similar condensation reactions with alkyl and aryl isothiocaynates. [Pg.86]

The effects of sex and age on the disposition of alendronate [23, R = OH, R = (CH2)3NH2l were studied in rats. The uptake in old animals was lower than that in young animals by a factor of 2-3. Alkylation of the amine enhanced further the activity as in dimethyl pamidronate [23, R = OH, R = (CH2)2NMe2] Heterocyclic derivatives containing a pyridine (24), imidazole (25) or pyrrolidine ring (26) were even more... [Pg.771]

Burow et al. (96) recently explored the utility of liquid SO2 for the removal of organic sulfur from Eastern bituminous coals. Liquid SO2 is supposed to be an excellent solvent for aromatic heterocyclic and alkyl sulfides derived from coal. They have considered the mild Lewis acid characteristics of SO2 and presented the following scheme for reaction... [Pg.1052]

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products. [Pg.2577]

Two synthetic bridged nitrogen heterocycles are also prepared on a commercial scale. The pentazocine synthesis consists of a reductive alkylation of a pyridinium ring, a remarkable and puzzling addition to the most hindered position, hydrogenation of an enamine, and acid-catalyzed substitution of a phenol derivative. The synthesis is an application of the reactivity rules discussed in the alkaloid section. The same applies for clidinium bromide. [Pg.309]

Nucleophilic reactivity of the sulfur atom has received most attention. When neutral or very acidic medium is used, the nucleophilic reactivity occurs through the exocyclic sulfur atom. Kinetic studies (110) measure this nucleophilicity- towards methyl iodide for various 3-methyl-A-4-thiazoline-2-thiones. Rate constants are 200 times greater for these compounds than for the isomeric 2-(methylthio)thiazole. Thus 3-(2-pyridyl)-A-4-thiazoline-2-thione reacts at sulfur with methyl iodide (111). Methyl substitution on the ring doubles the rate constant. This high reactivity at sulfur means that, even when an amino (112, 113) or imino group (114) occupies the 5-position of the ring, alkylation takes place on sulfiu. For the same reason, 2-acetonyi derivatives are sometimes observed as by-products in the heterocyclization reaction of dithiocarba-mates with a-haloketones (115, 116). [Pg.391]

Mercaptothiazoles with heterocyclic substituents in the 4-position have also been prepared (292, 508, 602). For example, N-alkyl-2-benzimidazolyl chloromethylketones (169) give the corresponding 2-mercaptothiazole derivatives (170) with R, = H, Me, CHjPh, Ac, COPh and R2==H, Me, 5,6-dichloro (Scheme 86) (602). [Pg.265]


See other pages where Heterocyclic derivatives alkylation is mentioned: [Pg.83]    [Pg.333]    [Pg.313]    [Pg.90]    [Pg.517]    [Pg.83]    [Pg.402]    [Pg.83]    [Pg.237]    [Pg.189]    [Pg.156]    [Pg.632]    [Pg.87]    [Pg.333]    [Pg.69]    [Pg.3]    [Pg.107]    [Pg.332]    [Pg.33]    [Pg.51]    [Pg.185]    [Pg.64]    [Pg.266]    [Pg.49]    [Pg.305]    [Pg.168]   
See also in sourсe #XX -- [ Pg.99 , Pg.299 ]




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Heterocycles alkylation

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