Chlorinations with Carbon Tetrachloride under Conditions of Phase Transfer Catalysis.

Lauritzen, Stein Erik; Rømming, Christian; Skattebøl, Lars; Vallén, Staffan; Enzell, Curt R.

doi:10.3891/acta.chem.scand.35b-0263

Cited by 20 publications

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“…The failure of 4b to be detected as a product from the treatment of 4 with CBrCl 3 or CBr 4 in KOH-t-BuOH was originally associated with the possibility that it was indeed formed, but was reductively debrominated back to 4-R-anion by reaction with the Cl 3 Cgenerated in these halogenations (see Scheme 1). Such a possibility seemed reasonable in light of the abundance of Brwe found after many reaction attempts and from the reductive debromination of R-bromobenzhydryl phenyl sulfone (7b) and R,R-dibromobenzyl phenyl sulfone (10b) 7 with Cl 3 C -. However, this suggestion was ruled out: 4b was quantitatively recovered when treated with Cl 3 C -(CHCl 3 -KOH-t-BuOH) at 25 °C.…”

Section: Resultsmentioning

confidence: 96%

“…α,α-dichlorobenzyl phenyl sulfone ( 10a ) was easily prepared in high yields from 10 treated with CCl 4 in KOH− t- BuOH or with C 2 Cl 6 −aq NaOH under phase-transfer catalysis. It was reported by Skattebøl et al that a 12-h treatment of 10 at 25 °C with a large excess of CBrCl 3 in 50% aq NaOH−CH 2 Cl 2 under P-T-C conditions (TEBA) produced α,α-dibromobenzyl phenyl sulfone ( 10b ) and the corresponding α-bromo-α-chloro sulfone. Since we previously found that 10b was the only product when 10 was treated with CBrCl 3 −KOH− t- BuOH for a very short time, we believed that reversibility of the brominations, and subsequent chlorination, was responsible for the formation of the α-chloro-α-bromo sulfone.…”

Section: Resultsmentioning

confidence: 99%

“…The greater effectiveness of the benzhydryl group than the isopropyl group in promoting anion formation was exhibited by the halogenations of the benzhydryl aryl sulfones. Conversion of benzhydryl phenyl sulfone (7) to its R-chloro sulfone 7a in theoretical yield required only a 30-min treatment with CCl 4 -KOH-t-BuOH at 3 °C. Even more impressive, the R-bromo sulfone 7b was obtained in over 90% yield upon treatment of 7 with CBrCl 3 at 0 °C for only 10 min.…”

Section: Resultsmentioning

confidence: 99%

“…(a) With C 2 Cl 6 in Aqueous NaOH Under Phase-Transfer Catalysis. Sulfone 10 was prepared as reported, mp 147−148 °C. A mixture of 10 (0.10 g, 0.4 mmol), C 2 Cl 6 (0.31 g, 1.3 mmol), Aliquat 336 (0.01 g, 0.025 mmol), 2 mL of CH 2 Cl 2 , and 50% aq NaOH (0.65 mL, 12 mmol) was stirred for 12 h. Water and CH 2 Cl 2 were then added and the organic layer was separated, dried, and concentrated as white crystals of 10a (0.12 g, 93% yield) with mp 151−152 °C (lit .…”

Section: Methodsmentioning

confidence: 99%

“…r-Chlorobenzhydryl Phenyl Sulfone (7a). Benzhydryl phenyl sulfone (7) was prepared via the sulfide as reported; 24 white needles, mp 186-187 °C (ethanol; lit. mp 187-188 °C).…”

Section: Reaction Of Cbrcl 3 With Koh-t-buoh and With T-bu-o-li-t-buohmentioning

confidence: 99%

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Unexpected Differences in the α-Halogenation and Related Reactivity of Sulfones with Perhaloalkanes in KOH−t-BuOH

et al. 2002

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Most alkyl phenyl sulfones are readily alpha-chlorinated with CCl(4) and alpha-brominated with CBrCl3 in KOH-t-BuOH via radical-anion radical pair (RARP) reactions. While isopropyl mesityl sulfone (4) is easily alpha-chlorinated with CCl(4), it was completely recovered when treated with the more reactive CBrCl3. Subsequent investigations showed the latter result to be due to the poor acidity of 4 together with the rapid depletion of CBrCl3 and KOH by their reaction with each other, and led to a variety of other important results. 4-Hydroxyphenyl isopropyl sulfone (6) is unreactive with either CCl4 or CBrCl3 in KOH-t-BuOH, its phenoxide anion strongly reducing the electronegativity of the sulfonyl group, thereby inhibiting alpha-anion formation. This effect is reversed by the electron-withdrawing influence of two alpha-phenyls, so that benzhydryl 4-hydroxyphenyl sulfone (8) is readily alpha-halogenated in KOH-t-BuOH with CCl4 or CBrCl3. On further contact with KOH-t-BuOH the alpha-halogenated sulfones from 8 are decomposed into benzophenone and phenol. While the alpha-halogenated derivatives of 4-methoxyphenyl benzhydryl sulfone (9) are stable to base, they are decomposed even under mildly acidic conditions into 4-methoxyphenyl 4-methoxybenzenethiolsulfonate (9c), phenol, and benzophenone. Mono-alpha-halogenation of benzyl phenyl sulfone (10) enhances the rate of the subsequent halogenation, so that alpha,alpha-dihalogenation is attained while much substrate is still present and the mono-alpha-halogenated product is not detected. The ease of reductive debromination of alpha-bromo sulfones with Cl3C- was correlated with the stability of the formed alpha-anions, explaining the success with alpha-bromobenzylic sulfones but failure with alpha-bromoalkyl sulfones. In the presence of air and the absence of competing halogenation, formation of the alpha-anions of alkyl aryl sulfones is quickly accompanied by oxidative cleavage by atmospheric O2, leading to the formation of arenesulfonyl alcohols, arenesulfonyl halides, and haloarenes.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…r-Chlorobenzhydryl Phenyl Sulfone (7a). Benzhydryl phenyl sulfone (7) was prepared via the sulfide as reported; 24 white needles, mp 186-187 °C (ethanol; lit. mp 187-188 °C).…”

Section: Reaction Of Cbrcl 3 With Koh-t-buoh and With T-bu-o-li-t-buohmentioning

confidence: 99%

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Unexpected Differences in the α-Halogenation and Related Reactivity of Sulfones with Perhaloalkanes in KOH−t-BuOH

et al. 2002

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The Ramberg‐Bäcklund Reaction

Taylor

Casy

2003

Organic Reactions

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The base‐mediated conversion of alpha‐halosulfones into region‐defined alkenes was first described by Ludwig Ramberg and Birger Backlund. This transformation has proved to be of wide synthetic value and is known as the Ramberg‐Backlund reaction (RBR). The facile nature of the RBR is surprising given the difficulties encountered when attempting to carry out nucleophilic substitution reactions on alpha‐halosulfones. In contrast to halogens adjacent to carbonyls and related electron‐withdrawing groups, polar, steric and field effects appear to combine leading to the marked deactivation of alpha‐halosulfones. The stereochemical outcome of the reaction was also unexpected: a predominance of Z‐alkenes is often observed with relatively weak bases, whereas stronger bases tend to favor E‐alkenes. The mechanism of the RBR was therefore the subject of intense interest, particularly in the 1950s and 1960s. From the synthetic viewpoint, the RBR is attractive for a number of reasons, for example, the accessibility of the precursor sulfide and sulfones; the conjunctive nature of the process; the unambiguous location of the resulting double bonds, among others. Organic sulfones are readily available, but the preparation of alpha‐halosulfones can be problematic. In view of this, perhaps the most significant synthetic advance concerning RBR has been the development of Meyer's modification, which involves in‐situ halogenation‐RBR sequence and enables sulfones to be converted directly into alkenes. This chapter discusses the mechanism of RBR, its scope and limitations, applications of the reaction in natural product synthesis, and comparison of the RBR with related procedures. Representative experimental procedures are also given.

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Formation of Carbon–Halogen Bonds (Cl,Br,I)

Sasson

2009

Patai's Chemistry of Functional Groups

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Introduction Halogenation in Presence of Solid Supports or Catalysts Halogen Exchange and Transhalogenation Reactions Oxyhalogenations Cohalogenation and Mixed Halogenation Halogen–Halogen Reagents Carbon–Halogen Reagents Nitrogen–Halogen and Phosphorus–Halogen Reagents Oxygen–Halogen Reagents Sulfur–Halogen Reagents Silicon–Halogen Reagents Halogenation with Metal Halides and Halodemetallation Halogenation in Special Environments Carbon–Halogen Bond Formation by Extrusion of CO , CO 2 or SO 2 Ring Opening of Oxiranes

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Chlorinations with Carbon Tetrachloride under Conditions of Phase Transfer Catalysis.

Cited by 20 publications

References 0 publications

Unexpected Differences in the α-Halogenation and Related Reactivity of Sulfones with Perhaloalkanes in KOH−t-BuOH

Unexpected Differences in the α-Halogenation and Related Reactivity of Sulfones with Perhaloalkanes in KOH−t-BuOH

The Ramberg‐Bäcklund Reaction

Formation of Carbon–Halogen Bonds (Cl,Br,I)

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