Basicity Carbinoles

Anionotropy and prototropy are, obviously, processes that mutually oppose each other. The more polar the C—OH bond in (5), i.e., the more the equilibrium (5) (4) will favor (4) [or in other words, the stronger the base (5) ], the less probable will be the prototropic change (5) (7). Anionotropy and prototropy, i.e., the three tautomeric forms, could only occur simultaneously for moderately basic carbinol-amines, since only these could be amphoteric. 

The polarity of the C—-OH bond, i.e., the basicity of the carbinol-amine, depends on its structure, particularly on the stability of the ring system (degree of aromatic character), and the electron affinity of the substituents on nitrogen and carbon. Of course, external factors also play an important role in the equilibrium temperature, polarity of the solvent, and presence or absence of catalysts (the solvent can also act as a catalyst). 

The oxidation by basic permanganate of phenyltrifluoromethyl carbinols which has the same rate law as benzydrol, is characterised by very large primary kinetic isotope effects (c/. Cr(VI) p. 307). 

Chlormadmone acetate (137), is an extremely potent orally active progestin. Treatment of this compound with basic sodium borohydride serves to reduce the ketone at C-3 to the corresponding 3-carbinol (138 the regioselectivity is presumably due... 

Additional examples of the Sonogashira reactions of pyridine triflates include coupling of 2-pyridyltriflate and 3-hydroxy-3-methylbut-l-yne to afford alkyne 141 [114], The carbinol adduct could be readily unmasked to give 2-ethynylpyridine via a basic-catalyzed retro-Favorsky elimination of acetone. Due to the volatility of 2-ethynylpyridine, use of a high boiling liquid such as paraffin oil for the basic hydrolysis made the distillation more convenient [115]. 

Behaviour towards Alkalis.—Add a few drops of sodium hydroxide solution to the aqueous solution of a basic triphenylmethane dye. For a short time the colour remains unchanged, but soon fades and at the same time a faintly coloured flocculent precipitate separates. In all cases this is the carbinol to which repeated reference has already been made when pure it is colourless. In the case of crystal violet the carbinol is [(CHg N.CgHJjCOH. 

A more recent synthesis for (14-9) takes quite a different course. The first step comprises the displacement of one of the halogens in 1,4-dibromobenzene by the alkoxide from A-2-hydroxyethylpyrrolidine (15-2) in the presence of 18-crown ether to afford (15-3). Condensation of the lithium salt from (15-3) with 6-methoxy-tetralone (15-4) followed by dehydration of the initially formed carbinol give the intermediate (15-5), which incorporates the important basic ether. Reaction of that compound with pridinium bromide perbromide leads to the displacement of the vinylic proton by halogen and the formation of bromide (15-6). Condensation of that product with phenylboronic acid in the presence of a tetrakistriphenyl-phosphine palladium catalyst leads to the coupling of the phenyl group by the formal displacement of bromine. The product (14-9) is then taken on to lasoxifene (14-11) as above [16]. 

After addition of the acetaldehyde solution is complete, the product is decomposed by pouring the reaction mixture on to 2 kg. of cracked ice. The excess magnesium may be removed conveniently by decantation at this point. The basic magnesium halide is dissolved by addition of about 11. of 15 per cent sulfuric acid. The ether solution is separated, and the aqueous layer is extracted with four 150-cc. portions of ether. The ether solutions are combined, dried over 25 g. of calcined potassium carbonate, filtered and fractionally distilled, using a short column. The methyl isopropyl carbinol distils at no-ni.50. The fraction boiling 37 -1090 should be dried and refractionated. The total yield is 210-215 g. (53-54 per cent of the theoretical amount) (Note 7). 

In the spectra of dilute solutions, only 240 shows intramolecular hydrogen bonding, and all four isomers show strong Bohlmann bands. Hence all were assigned trans-ring conformations. These conformations were further supported by (i) NMR data—primarily the chemical shift and bandwidth of the carbinol proton (ii) pKa values—240 was found to be considerably more basic than 241, whereas there was less difference between the 7-hydroxy compounds (iii) chemical data—the product isomer ratios obtained when the conditions for the reduction of the ketones were altered were in accordance with the above assignments. The... 

Increasing junction potential also increased carbinol yield as was seen with aldehyde reductions. In basic electrolytes or in nonaqueous media, the dimer 50 was the major product. 

The triarylmethane dyes were also very important leather dyes in the past. The central carbon is sp2-hybridized (triarylmethine) and can add a hydroxyl group to form the respective carbinol base with spP-hybridized carbon. The dyes react like Lewis acids and some species act as pH indicators (e g., phenolphthaleine). The term cationic dyes is therefore recommended for this dye class instead of basic dyes. Nowadays only the sulfonated triphenylmethine dyes are used for leather. 

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