Addition Of Bromine Chloride Research Articles

ChemInform Abstract: Addition of Bromine Chloride and Iodine Monochloride to Carbonyl‐Conjugated, Acetylenic Ketones: Synthesis and Mechanisms.

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Addition of bromine chloride and iodine monochloride to carbonyl-conjugated, acetylenic ketones: synthesis and mechanisms.

The reactions of 3-butyn-2-one (1), 3-hexyn-2-one (2), and 4-phenyl-3-butyn-2-one (3) with bromine chloride (BrCl) and iodine monochloride (ICl) in CH(2)Cl(2), CH(2)Cl(2)/pyridine, and MeOH are described. The data show that the major products in CH(2)Cl(2) are (Z)-AM (anti-Markovnikov) regioisomers. With the exception of 3 and ICl, the (E)-AM regioisomers predominate when pyridine was added as an acid scavenger. Minor amounts of the M regioisomers were formed with 1 and 2 and BrCl. The percentage of M regioisomer increased significantly with 1 and BrCl in MeOH, but MeOH had little affect on the other reactions. Isolation and stability of the products are discussed. Detailed evidence for the structures of the products, involving a combination of MS, (1)H and (13)C NMR, and IR, is presented; HRMS analyses are provided as proofs for all of the products. The acid-catalyzed mechanism and the halonium ion mechanism are considered as possible pathways in the formation of the products.

Effect of pyridine on the regio- and stereo-chemistry in the addition of bromine chloride to α,β-unsaturated aldehydes and ketones

The addition of bromine chloride (BrCl) in methylene dichloride (CH2Cl2) in the presence and absence of acid scavengers such as pyridine to the following α,β-unsaturated aldehydes, ketones and esters is described: acrylaldehyde 1, methyl vinyl ketone 2, phenyl vinyl ketone 3, (E)-crotonaldehyde 4, (E)-pent-3-en-2-one 5, (E)-4-phenylbut-3-en-2-one 6, 4-methylpent-3-en-2-one 7, methyl isopropenyl ketone 8,3-phenylbut-3-en-2-one 9, cyclohex-2-enone 10, methyl acrylate 11, (E)-methyl crotonate 12 and methyl methacrylate 13. The majority of the aldehydes and ketones gave primarily anti-Markovnikov (AM) bromo chloride regioisomer in the absence of pyridine. In most cases the Markovnikov (M) regioisomer increased significantly in the presence of pyridine. Addition of BrCl to 4, 5, 6 and 10 became stereospecific (erythro) in the presence of pyridine. The stereospecificity of addition to ester 12 was high with or without pyridine. These data were interpreted as follows: in the absence of an acid scavenger, an acid-catalysed reaction is involved, initiated by attack of proton on the carbonyl oxygen. When traces of acid are removed by an acid scavenger, the reactions proceed through a bromonium ion–chloride ion intermediate. The esters reacted only via a bromonium ion giving essentially the same mixture of regioisomers with and without acid scavenger.

Selective Bromochlorination of endo-1,4-Dibromotricyclo[5.2.1.02,6]deca-3,8-diene-5,10-dione 10-Ethylene Acetal at the Conjugated Carbon-Carbon Double Bond

Exposure of (1) to bromine in thionyl chloride/ dimethylformamide produced (5), the result of regio- and stereo-selective addition of bromine chloride across the carbonyl-conjugated double bond. The structure of (5) was determined by X-ray crystallography, and its mode of formation is discussed in terms of the carbonyl attack mechanism.

ChemInform Abstract: BROMOCHLORINATION OF ALKENES WITH DICHLOROBROMATE(1‐) ION. II. REGIO‐ AND STEREOCHEMISTRY FOR THE BROMOCHLORINATION OF 1‐PHENYLPROPENES WITH DICHLOROBROMATE(1‐) ION

AbstractWährend die Bromchlorierung der isomeren Phenylpropene (I) mit Bu4NBrCl2 (II) in vollständig anti‐stereospezifischer, jedoch nicht‐regiospezi‐ Fischer Weise erfolgt [‐ threo‐ bzw. erythro‐Isomeren der Addukte (III)+(IV)], liefert die Bromchlorierung mit BrCl (V) nicht‐stereospezifische, aber regiospezi?‐ sche Addukte [‐ threo + erythro‐Verbindungen (III)].

Bromochlorination of Alkenes with Dichlorobromate(1–) Ion. II. Regio- and Stereochemistry for the Bromochlorination of 1-Phenylpropenes with Dichlorobromate(1–) Ion

Abstract The bromochlorinations of 1-phenylpropenes with tetrabutylammonium dichlorobromate(1–) in aprotic solvents (dielectric constants 5–36) were found to be completely anti stereospecific and nonregiospecific, although Markownikoff adduct was mainly formed. In marked contrast, addition of molecular bromine chloride to the same alkenes was found to give nonstereospecific and regiospecific adducts. These results suggest that the addition of bromine chloride in the form of (n-C4H9)4NBrCl2 involves a rate- and product-determining attack of a chloride ion to a three-center bound π complex.

Addition of halogens to 3-fluoro-1-hexyne

A few years ago we reported on the addition of bromine chloride (BrCl) to 1-hexene and 1-hexyne. 1-hexyne reacts with BrCl to give Markownikoff and anti -Markownikoff projects 1a and 2a in a 90:10 ratio respectively. ▪ Reaction of 3-fluoro-1-hexyne with bromine and chlorine give cis - and trans -1,2-dihalo-1-hexenes. Addition of BrCl to 3-fluoro-1-hexyne gives a major project which is tentatively assigned the structure 2b . Thus reaction of BrCl with 1-hexyne and 3-fluoro-1-hexyne give intermediates 3 and 4 respectively. A possible free radical process or radical competing pathway for the reactions of halogens with 3-fluoro-1-hexyne is also considered.

On steroids. Part 209. Formation of 6β-bromo-5-chloro-5α-cholestan-3β-ol on addition of bromine chloride to cholesterol

On treatment with phosphorus tribromide 3β-acetoxy-5-chloro-5α-cholestan-6β-ol (6) yielded 3β-acetoxy-6β-bromo-5-chloro-5α-cholestane (4) which was converted into the corresponding 3β-hydroxy-derivative (2) and the 3-oxo-derivative (14). Dehydrohalogenation of compound (14) gave the known 6β-bromo-4-cholesten-3-one (15). Compound (2) was found as a product of bromine chloride addition to cholesterol. Results are discussed in terms of stereochemical control of addition of an electrophile to the Δ5-double bond.