Phosphorus oxychloride trifluoride

Apparatus. The generator employed is shown in fig. 10. There are six important points. (1) The column. <4 is designed so that throttling is avoided it is at least 2 ft. long and surmounted by a reflux doublesurface water-condenser B. (2) A Perkin triangle (air-cooled), inserted between the down-condenser and the traps, enables any phosphorus oxychloride which distils to be removed. (3) It is convenient to have three traps, viz. C, ice and salt D, acetone and carbon dioxide E, liquid air. (4) The intermittent addition of the solid antimony trifluoride presents a problem. The mechanical solid feed... 

Procedure. Finely powdered antimony trifluoride is placed in the reservoir of the feed. Phosphorus oxychloride and then antimony pentachloride are placed in the reaction vessel. The temperature of the bath is maintained, thermostatically, at 75° and the pressure kept at 190-200 mm., and the antimony trifluoride is then added slowly from the feed. The distillates in the traps are united and fractionated. The distillate, up to b.p. 90°/760 mm., is collected and carefully refractionated, giving pure phosphorus oxydichlorofluoride, b.p. 54° (20 per cent yield). 

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). 

It has long been apparent that when the acid concentration is too low, the Schiff base is hydrolyzed back to its components and, when it is too high, extensive decomposition results. In order to obviate the decomposition problem, numerous acidic reagents have been tried. Some of these are polyphosphoric acid-phosphorus oxychloride,2 polyphosphoric acid,8 and boron trifluoride-trifluoroacetic anhydride.8 Some improvement has been observed, but many yields are still poor. 

Isophyllocladene epoxide, on treatment with boron trifluoride etherate, furnishes a mixture of two ketones a phyllocladan-15-one and a neoatisiranone (87). The enantiomer of this compound has been partially synthesized from neoatisirene. Neoatisiranol, on treatment with phosphorus oxychloride in pyridine, undergoes a rearrangement to the olefin (88). 

As described previously, thiazolines are versatile intermediates to thiazoles. In addition, thiazoline rings are structural motifs found in numerous natural products. Among a variety of methods for the construction of thiazolines, the cyclodehydration protocol is perhaps most popular. Bis(2-methoxyethyl)aminosulfur trifluoride (Deoxo-Fluor) is used as the cyclo-dehydrating agent for the conversion of 3-hydroxy thioamide 60 to the bis(thiazoline) 15 <04H(63)773>. A more recent protocol for the cyclodehydration of P-hydroxy thioamides to thiazolines involves pyridine-buffered phosphorus oxychloride as exemplified by the formation of 62 from 61 <04JA12897>. 

Phosphorus oxychloride may be used in place of zinc chloride, and this is recommended for cases where the latter has not sufficient condensing action owing to the low solubility of its amine adduct.884 Boron trifluoride etherate was found to be a particularly active catalyst for condensation of 9-fluorenone with aromatic amines.885... 

A distinctly different method of synthesizing the esters of phosphorofluoridic acid consisted in the partial fluorination of phosphorus oxychloride with antimony trifluoride (using a specially designed apparatus and phosphorus pentachloride as catalyst) to give phosphorus oxydichlorofluoride, POClaF. In the latter compound the chlorine atoms proved to be much more reactive than the fluorine atom, and with an alcohol the dialkyl phosphorofluoridate was readily obtained in high yield. ... 

Antimony pentachloride Boron trichloride gas Boron trifluoride gas Boron trifluoride ethyl etherate Boron trifluoride methyl etherate Bromine trifluoride Phosphorus oxychloride Phosphorus pentachloride Phosphorus tribromide... 

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