Benzoyl chloride-pyridine complex

The benzoyl chloride-pyridine complex also reacts with hydrogen sulfide at about -20°C to afford an 85% yield of dibenzoyl sulfide (Eq. 5). 

In a typical Knof procedure, 3jS-hydroxyandrost-5-en-17-one acetate is epoxidized with perbenzoic acid (or m-chloroperbenzoic acid ) to a mixture of 5a,6a- and 5)5,6)5-epoxides (75) in 99 % yield. Subsequent oxidation with aqueous chromium trioxide in methyl ethyl ketone affords the 5a-hydroxy-6-ketone (76) in 89% yield. Baeyer-Villiger oxidation of the hydroxy ketone (76) with perbenzoic acid (or w-chloroperbenzoic acid ) gives keto acid (77) in 96% yield as a complex with benzoic acid. The benzoic acid can be removed by sublimation or, more conveniently, by treating the complex with benzoyl chloride and pyridine to give the easily isolated )5-lactone (70) in 40% yield. As described in section III-A, pyrolysis of j5-lactone (70) affords A -B-norsteroid (71). Knof used this reaction sequence to prepare 3)5-hydroxy-B-norandrost-5-en-17-one acetate, B-noran-... 

There have been a number of studies of the behaviour of benzimidazolium species with nucleophiles, and ring opening is especially easy when there is a l-(2,4-dinitrophenyl) substituent. Even weak bases such as aniline or pyridine can effect the transformations. Under the influence of benzoyl chloride in aqueous alkali, 1,2-disubstituted benzimidazoles are cleaved in a rather complex reaction. Provided that a methylene or methyl group is present at C-2, compounds of type (110) result (Scheme 49) (74CRV279). 

Reaction of acetylene itself with the [HFe(CO)4] anion under pressure gives a 45% yield of a yellow solid of composition Fe2CioH40g, volatile at 70-80° C/0.1 mm [186). For several years the structure of this compound was a mystery. Further work demonstrated its ability to act as a weak acid, forming the air-sensitive anion [Fe2CioH20g] which reacted with dimethyl sulfate to form a dimethyl derivative [187). The parent complex Fe2CioH40g could also be benzoylated with benzoyl chloride in the presence of pyridine [187). 

Acetyl- 8 benzoyl- " 489-90 nd various other acylpyridinium chlorides 86-8, 491-3 sometimes of doubtful purity (because of their very ready hydrolysis or of contamination with pyridinium chloride), have been described. Salts of benzoylpyridinium with complex metal anions are also known 94. Covalent structures, with the chlorine atom at C(2) or C(4) of the pyridine ring, have been suggested for the adducts from pyridine and the nitrobenzoyl chlorides , but the ionic character of 1-acetylpyridinium chloride is affirmed by measurements of its electrical conductivity in sulphur dioxide solution . 

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