Titanium(1V) chloride in the presence of an oxidizing reagent such as peroxytrifluoroacetic acid is shown to chlorinate a variety of aromatic substrates. The substitution orientation patterns suggest that the reaction is an electrophilic substitution process, which possibly involves the intermediacy of hypochlorous acid. Chlorination fails to occur with ring systems bearing strongly deactivating substituents, but it proceeds very cleanly and in high yield with activated rings, e.g. phenol. The reaction conditions are mild and are adaptable for bromination or iodination as well as chlorination.On montre que le chlorure de titanium(IV), en presence d'un agent oxydant tel I'acide peroxytrifluoroacCtique, permet d'introduire un chlore sur plusieurs substrats aromatiques. Les modtles d'orientation de la substitution suggerent que la reaction est un procede de substitution electrophile, qui implique possiblement I'intermediaire de I'acide hypochloreux. II n'y a pas de substitution de chlore sur les noyaux portant des substituants fortement desactivants, mais elle se produit facilement, avec de bons rendements, dans le cas de noyaux actives, tel le phenol. Les conditions de rtaction sont douces et peuvent Btre adaptees pour la bromuration et I'ioduration, aussi bien que pour la chloruration.Canadian Journal of Chemistry, 50, 1233 ( 1 972) Halogenation of aromatic rings is one of the more thoroughly investigated organic reactions, and it has been discussed in a wealth of chemical literature (1). Most reactions of this type fall into four general classes, uiz. ( I ) reaction of electron-rich aromatic rings with molecular halogen; (2) reaction of less-activated rings with molecular halogen in the presence of a catalyst; (3) reaction of aromatic compounds with systems which furnish a positively charged halonium ion species (e.g. chlorine -silver acetate) ; and (4) direct halogenation of an aromatic molecule with halogen, apparently derived from reduction of a metal halide, but without the addition of any free halogen.Of these four general approaches, the lastmentioned has been studied relatively little, although the use of iron(II1) and antimony(V) chlorides as aromatic chlorinating agents has been known for over 100 years (2). Since that tion are known to occur (4, 5). In the nuclear chlorination of aromatic compounds with metal halides, various lines of evidence, including the predominant ortholpara orientation, point to an electrophilic substitution mechanism, although the actual attacking form of the metal halide is uncertain.Titanium(1V) chloride by itself has never been reported to chlorinate aromatic compounds, but it has been used as a catalyst and as a solvent in the chlorination of aromatic rings by other metal halides (6). Previously, we reported that titanium(1V) chloride, in the presence of peroxytrifluoroacetic acid or m-chloroperbenzoic acid, will chlorinate aromatic compounds (7). In the present paper, we report further examples of aromatic chlorination with this system and present evidence for a propose...

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The photochemical transformations undergone by 2-cyano-2-methylcycloheptanone (1) and 2-cyano-2-methylcyclohexanone (2) have been studied in methanol and aqueous dioxane. In the former solvent, 1 is isomerized to three products in the ratio 78:8:13, corresponding to the enals 3a and 3b, and a new ring expansion product 4, respectively. In aqueous dioxane, the cyclic imide 6 was obtained in 18% yield. Cycloalkanone 2 in methanol produces four products in the ratio 61:30:7:1, these being the isomeric enals 8a and 8b, the ester 9, and the ring expansion product 10. No imide related to 6 could be obtained from irradiation of 2 in aqueous dioxane.

Irradiation of two a-cyanocycloalkanones gives the corresponding enals as major products, together with ring expanded products with incorporation of a nitrogen atom into the ring.PHOTOCHEMICAL ring expansions of suitably substituted cyclic ketones leading to larger ring ketones and macrolides have gained recent attention.1 We report on our studies of the cyclic K-cyano-ketones (la) and (1 b) whicn undergo a novel ring enlargement with incorporation of a nitrogen atom into the ring on irradiation.Photolysis (Hanovia 450 W Hg high pressure lamp) of a 1-2% degassed solution of (1a)Z in methanol followed by preparative g.1.c. gave the E t aldehyde (2a) (30%) [Vmax

Die Bestrahlung des Cycloheptanons (I) in Methanol liefert neben einem Isomerengemisch des Z‐ und E‐Aldehyds (II) das Produkt der Ringerweitemng (III).