Phosphorus Oxychloride-Zinc Chloride

Related Reagents. Bis(trichloromethyl) Carbonate Phos-phorus(V) Oxide Phosphorus Oxychloride-Zinc(II) Chloride Thionyl Chloride p-Tolyl Vinyl Sulfoxide Trichloromethyl Chloroformate. 

The difficulties encountered in the synthesis of 2-alkyl- and 2-aryl-substituted selenazoles lie principally in the preparation of the corresponding selenoamides. In this respect, a method is worthy of note in which the use of selenoamides is dispensed with. For this, a nitrile, a hydrogen selenide, and an a-halogenoketone are reacted together in the presence of a condensation catalyst. Phosphorus oxychloride, alone or mixed with zinc chloride or phosphorus trichloride, is specially suitable. The yields of the corresponding 2-alkylseIenazoles are up to a maximum of 25%,... 

Phenyl cinnamate and other phenolic esters have been prepared by heating the acid and phenol in the presence of phosphorus oxychloride,1 and by heating the acid anhydride and phenol together in the presence of a dehydrating agent such as fused zinc chloride or anhydrous sodium acetate.2 Phenyl cinnamate has also been prepared by the careful distillation of phenyl fumarate.3... 

Thenaldehyde (thiophene-2-carbaldehyde) is readily available via the Vilsmeier-Haack reaction of DMF with thiophene catalyzed by phosphorus oxychloride. The Sommelet reaction with 2-chloromethylthiophene also gives reasonable yields (63AHC(l)l). Likewise, thiophene is readily acylated with acyl anhydrides or acid chlorides (equation 14), using mild Friedel-Crafts catalysts, such as tin(IV) chloride, zinc chloride, boron trifluoride, titanium tetrachloride, mercury(II) chloride, iodine and even silica-alumina gels or low-calcium-content montmorillonite clays (52HC(3)l). 

Zinc chloride is also used in an alternative approach to 4-hydroxycoumarins, in which malonic acid is used as the 1,3-dicarbonyl component, although additionally the presence of phosphorus oxychloride is vital to success (60JOC677). 

The reaction of 1,3-dihydroxynaphthalene with 3,3-dimethylacrylic acid in the presence of phosphorus oxychloride and zinc chloride yields only 9-hydroxy-2,2-dimethyl-benzo[/]chroman-4-one (585). 2,7-Dihydroxynaphthalene similarly yields the angular ben-zochromanone (586) rather than the alternative linear product (79RRC59). 

Ketone Method. In the ketone method, die central carbon atom is derived from phosgene. A diarylketone is prepared from phosgene and a tertiary arylamine and then condenses with another mole of a tertiary arylamine (same or different) in the presence of phosphorus oxychloride or zinc chloride. The dye is produced directly without an oxidation step. Thus, ethyl violet CT Basic Violet 4, is prepared from 4.4 -bis(diethy]amino)benzophenone with diethylaniline in the presence of phosphorus oxychloride. This reaction is very useful for the preparation of unsymmetrical dyes. 

Acylation. Acylation is the most reliable means of introducing a 3-substituent on the indole ring. Because 3-acyl substituents can be easily reduced to 3-alkyl groups, a two-step acylation—reduction sequence is often an attractive alternative to direct 3-alkylation. Several kinds of conditions have been employed for acylation. Very reactive acyl halides, such as oxalyl chloride, can effect substitution direcdy without any catalyst. Normal acid chlorides are usually allowed to react with the magnesium (15) or zinc (16) salts. The Vilsmeier-Haack conditions involving an amide and phosphorus oxychloride, in which a chloroiminium ion is the active electrophile, frequendy give excellent yields of 3-acylindoles. 

Alkyl chlorides have been obtained by the direct chlorination of hydrocarbons 1 and by the addition of hydrogen chloride to olefines.2 However, they have usually been prepared from the corresponding alcohol by the action of a number of reagents, such as dry hydrogen chloride,3 dry hydrogen chloride in the presence of zinc chloride,4 phosphorus trichloride,3 phosphorus oxychloride,6 phosphorus pentachloride,7 phosphorus trichloride... 

Zinc chloride (1.47 mol) and phosphorus oxychloride (7.71 mol) were mixed and heated 30 minutes at 50°C, then treated with 2,3-dimethoxybenzoic acid (1.37 mol). The mixture was stirred 1 hour, then treated with phlorglucinol (1.58 mol), stirred an additional hour, and cooled to ambient temperature. The reaction contents were then poured into 101 ice water and stirred 20 minutes. The aqueous layer... 

Finally, treatment of amides with phosphorus oxychloride gives Vilsmeier complexes, which are often formulated as A-alkylated imidoyl chlorides (59). Irrespective of their precise nature, it has been found that they can be converted very efficiently to aldehydes by reduction with zinc followed by aqueous work-up (Scheme 17). Although the method has only been used for benzaldehyde and a number of chlorinated and brominated analogs, the yields reported are consistently high (87-97%). ... 

Pictet-Hubert reaction. Phenanthridine cychzation by dehydrative ring closure of acyl-o-amino-biphenyls on heating with zinc chloride at 250-300C or with phosphorus oxychloride in boiling nitrobenzene. 

The standard methods for the synthesis of xanthones are via the benzophe-none 17 and diaryl ether intermediates 18 (Fig. 7). The intermediate ben-zophenone derivatives 17 can be obtained by condensation between an ortho-oxygenated benzoic acid and an activated phenol, in the presence of phosphorus oxychloride and zinc chloride (a) [44]. This intermediate is also accessible through condensation by the Friedel-Crafts acylation of appropriately substituted benzoyl chlorides with phenolic derivatives (b) [45]. Then the oxidative or dehydrative processes cause the cyclization of 2,2 -di-oxygenated ben-zophenone to xanthone (c) [46]. 

A. 7, -Diohloro-l-methylbieyclo[3.2.0]heptan-6-one. A 500-mL, two-necked, round-bottomed flask 1s equipped with a Teflon-covered magnetic stirring bar, a 250-mL pressure-equalizing addition funnel topped with a gas inlet, and a condenser connected to a Nujol-filled bubbler (Note 1). The system 1s flushed with nitrogen (Note 2). The flask 1s then charged with 10.0 g (ca. 150 nmol) of zinc-copper couple (Note 3), 200 mL of anhydrous ether (Note 4), and 10.5 mL (8.2 g, 100 mmol) of 1-methyl-1-cyclopentene (Note 5) and the addition funnel is filled with a solution of 13.4 mL (21.8 g, 120 mmol) of trlchloroacetyl chloride (Note 5) and 11.2 mL (18.4 g, 120 mmol) of phosphorus oxychloride (Note 6) 1n 100 mL of anhydrous ether. Magnetic... 

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