P-chlorobenzoates

This modification is illustrated by the preparation of p-chlorobenzoic anhydride from p-chlorobenzoyl chloride. 

Place a mixture of 17 -5 g. p-chlorobenzoyl chloride (1) and 50 ml. of dry pyridine (Section 11,47,22) in a loosely-stoppered 250 ml. flask and warm on a steam hath for 5 minutes. Pour the reaction mixture upon 100 g. of crushed ice and 50 ml. of concentrated hydrochloric acid. The anhydride separates out at once. When the ice has melted sufficiently, filter the mixture by suction. Wash the sohd with 15 ml. of methanol and then with 15 ml. of dry benzene. The yield of crude p-chlorobenzoic anhydride is 14 5 g. Recrystalhse from 250 ml. of dry benzene 13 g. of the pure anhydride, m.p. 192-193°, are obtained. 

B. p-Chlorobenzoic anhydride benzoic anhydride, p,p -di-ckloro-). A mixture of 17.5 g. (0.1 mole) of j -chlorobenzoyl chloride (Note 6) and 50 ml. (0.6 mole) of pyridine in a loosely stoppered 200 ml. flask is warmed on the steam bath for 5 min-... 

Chlorobenzene, electrostatic potential map of, 565 13C NMR absorptions of, 536 phenol from, 575 p-Chlorobenzoic acid, pKa of, 760... 

Benzoic m-Toluic (Benzoic acid, 3-methyl-] p-Toluic [Benzoic acid, 4-methyl-J 3,5-Dimcthylbcnzoic [Benzoic acid, 3,5-dimcthyl-] p-Chlorobenzoic [Benzoic acid, 4-chloro-] p-Bromobenzoic [Benzoic acid, 4-bromo-J Phthalic [ 1,2-Bcnzcncdicarboxylic acid] Toluene [Benzene, methyl-] (78) m-Xylene [Benzene, 1,3-dimethyl-] (82) />-Xylene [Benzene, 1,4-dimethyl-] (74) Mesitylene [Benzene, 1,3,5-trimethyl-] (82) p-Chlorotolueno [Benzene, l-ehloro-4-methyl-] (94) p-Bromotolucnc [Benzene, l-bromo-4-methyl-] (94) o-Xylene [Benzene, 1,2-dimethyl-] (64)... 

It is often possible in these cases to predict the correct isomer. In many cases, the groups already on the ring reinforce each other. Thus, 1,3-dimethylbenzene is substituted at the 4 position (ortho to one group and para to the other), but not at the 5 position (meta to both). Likewise the incoming group in p-chlorobenzoic acid goes to the position ortho to the chloro and meta to the carboxyl group. 

Treatment of methyl p-chlorobenzoate with an equivalent amount of commercial potassium silanolate 97 in abs. diethyl ether affords, after 4h, pure, anhydrous potassium p-chlorobenzoate in 84% yield and methoxytrimethylsilane 13 a. Trimethylsilyl trifluoroacetate reacts hkewise with sodium trimethylsilanolate 96 in THF to give sodium trifluoroacetate, in 98% yield, and hexamethyldisiloxane 7 [119] (Scheme 4.45). 

Many benzenesulfonamides have diuretic properties, particularly those having two such functions situated meta to one another. To some extent a carboxyl group can serve in place of one of the sulfonamido groups. Bumetanide (8) is such a substance. Chlorosulfonation of p-chlorobenzoic acid leads to 5, which is nitrated, and then converted to sulfonamide 6 with ammonia. 

The diuretic clopamide (35) is synthesized from p-chlorobenzoic acid (33) by chlorosulfonation and subsequent ammonia treatment to give 34. This is converted to its acid chloride with thionyl chloride and reacted with the desired hydrazine derivative... 

In 1988, Sharpless and co-workers reported that dihydroxylation was catalytically effected, with good enantioselectivity and remarkable ligand acceleration, when DHQD or DHQ p-chlorobenzoate... 

The intervention of an intermediate with the symmetry of a benzocyclopropenone (166, R = Cl) is also demanded by the formation of methyl p-chlorobenzoate in the photolysis of the lithio derivative 173 of the chlorosubstituted 3-p-tolylsulpho-nylamino-benzo-l,2,3-triazin-4-one128) ... 

Aldehyde 54 and the hydroxamic acids 55 were generated together in an acid-catalysed elimination reaction (Scheme 7 pathway (ii)). A crossover experiment indicated that esters are formed in a concerted rearrangement concomitant with the likely formation of the hydroxynitrene 57 (Scheme 7 pathway (iii)) while there is no evidence to date for the formation of hydroxynitrene, joint solvolysis of equimolar quantities of /V-acetoxy-/V-butoxy-/>-chlorobenzamide 26e and N- acetoxy-/V-benzyloxybenzamide 27a afforded significant quantities of butyl p-chlorobenzo-ate (36%) and benzyl benzoate (54%) as the only esters. This is an example of a HERON reaction, which has been identified in these laboratories as a characteristic rearrangement of bisheteroatom-substituted amides.32,33,42 43 155 158 Since ester formation was shown to prevail in neutral or low acid concentrations, it could involve the conjugate anion of the hydroxamic acid (vide infra).158... 

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