Ring contraction of 4-substituted 2,6-dichlorophenols. The crystal structure of 2,2,4α,5α-Tetrachloro-1α,3α-dihydroxycyclopentane-1,4-carbolactone

Abstract

Alkaline chlorination of the 4-alkyl-2,6-dichlorophenols (2b) and (2c) proceeds through ring contraction and halolactonization to form the 4α- alkyl-2,2,5α-trichloro-1α,3α-dihydroxycyclopentane-1,4-carbolactones (4b) and (4c). Under similar conditions, 2,4,6-trichlorophenol affords the analogous 2,2,4α,5α-tetrachloro-1α,3α-dihydroxycyclopentane-1,4- carbolactone (4a) in low yield, in addition to the Hantzsch acid (3a) as the major product. The acid (3a) upon further treatment undergoes chloro-lactonization to give the lactone (4a). The structures of the lactones (4b) and (4c) follow from spectroscopic comparison with (4a), the structure of which has been established by X-ray diffraction (C6H4Cl4O4 orthorhombic a 13.485(1), b 12.348(1), c 11.371(1) Ǻ, space group Pccn, Z 8, solved by direct methods and refined by block-diagonal and full-matrix least squares to R 0.031, Rw 0.043 for 1313 unique counter data with I/σ(I) ≥ 3.0).

Increased chloroform production from model components of aquatic humus and mixtures of chlorine dioxide/chlorine

“…The dichloro product (6) was shown to have a different GC retention time than obtained by the chlorination of resorcinol. That product, assigned the -dione structure (7), by Boyce and Hornig (10), gives an identical mass spectrum (Figure 2) [via loss of dichloroketene; 166 (37), 164 (59), 138 (61), 136 (100), 110 (39), 108 (26), 82 (46), 73 (82), 54 (70)] to that product obtained either by chlorination of 1,3-cyclopentenedione or by the reaction of 1 or 2 with chlorine dioxide.…”

“…(5) Additional chlorine dioxide results in the conversion of 5 to 6 (based on HPLC retention times), and if aqueous chlorine is added at this stage, no further degradation of 6 is observed. (6) The reduction of 5 with sodium borohydride and subsequent treatment with diazomethane or acetic anhydride gave a series of mono-, di-, and trimethylated or -acylated derivatives of a chloro-1,2,4-trihydroxybenzene (Scheme II). (7) There was the close correlation of the maximum observed in chloroform production, with the maximum in the formation of 5 (Table II).…”

“…Oxidants such as chlorine dioxide or chloramine have been suggested as alternatives, to be used singly or, in combination, with chlorine. If such alternatives are used, the chemical pathways for degradation of the organic components present in the water (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) would also be expected to be altered. Trihalomethanes (THM) represent a well-studied fraction from chlorine-induced chemical degradation, and several hydroxybenzoic and cinnamic acids, as commonly used model components of aquatic humus, were examined, for possible changes in THM production accompanying a variation in oxidant.…”

Chlorous acid oxidation of trifluoromethylphenols: cyclopentenolones by benzilic acid ring contraction

“…The solution was evaporated under reduced pressure (5 x lW3 mmHg) and the residue distilled in a Buchi apparatus (oven temp. 170 "C; 6 x mmHg) to give the bis silyl derivative (6) (1.77 2-Chloro-1 -hydroxy-3-oxo-2-triJIuoromethylcyclopentanecarboxylic Acid (7).-An excess of triethylsilane (4 ml, 25 mmol) was added to a stirred solution of the acid (4) (2 g, 8.2 mmol) in trifluoroacetic acid cooled in an ice-bath. After 1 h the ice-bath was removed and the solution was stirred for 48 h. The solution was evaporated under reduced pressure (bath temp.…”

“…After 1 h the ice-bath was removed and the solution was stirred for 48 h. The solution was evaporated under reduced pressure (bath temp. 60 "C, 1(F2 mmHg) and the residue was taken up in hexane and filtered to give the saturated acid (7) Oxidation of the Phenol (12).-Oxidation of the phenol (12) was carried out as described on a 5 g scale. Since most of the starting material remained unconsumed, the crude product was reoxidised using the same conditions.…”