New Reagent Systems for Electrophilic Chlorination of Aromatic Compounds: Organic Chlorine-Containing Compounds in the Presence of Silica

Smith, Keith; Butters, Michael; Paget, Walter E.; Nay, Barry

doi:10.1055/s-1985-31461

Cited by 33 publications

(16 citation statements)

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“…However, the process was not very selective towards the para-isomers. The highest para/ortho ratios were obtained in chlorination of tert-butylbenzene (85/15) and anisole (70/30) in tetrachloromethane (CCl 4 ) at 25 • C [32], but the regioselectivity was not very different from that in traditional chlorination reactions of such substrates. Successful regioselective bromination of indoles, benzimidazoles, β-carbolines, and iminodibenzyls was achieved using N-bromosuccinimide over silica.…”

Section: The Use Of Structured Solids To Influence the Halogenation Reactions Of Aromatic Compoundsmentioning

confidence: 96%

“…Our earliest attempts at controlling halogenation reactions of aromatic compounds by use of solid additives involved the use of silica [32][33][34][35][36][37]. For example, the chlorination of various monosubstituted benzenes using tert-butyl hypochlorite over silica resulted in the corresponding orthoand para-disubstituted benzenes.…”

Section: The Use Of Structured Solids To Influence the Halogenation Reactions Of Aromatic Compoundsmentioning

confidence: 99%

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Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

Smith

El‐Hiti

2021

Organics

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para-Selective processes for the chlorination of phenols using sulphuryl chloride in the presence of various sulphur-containing catalysts have been successfully developed. Several chlorinated phenols, especially those derived by para-chlorination of phenol, ortho-cresol, meta-cresol, and meta-xylenol, are of significant commercial importance, but chlorination reactions of such phenols are not always as regioselective as would be desirable. We, therefore, undertook the challenge of developing suitable catalysts that might promote greater regioselectivity under conditions that might still be applicable for the commercial manufacture of products on a large scale. In this review, we chart our progress in this endeavour from early studies involving inorganic solids as potential catalysts, through the use of simple dialkyl sulphides, which were effective but unsuitable for commercial application, and through a variety of other types of sulphur compounds, to the eventual identification of particular poly(alkylene sulphide)s as very useful catalysts. When used in conjunction with a Lewis acid such as aluminium or ferric chloride as an activator, and with sulphuryl chloride as the reagent, quantitative yields of chlorophenols can be obtained with very high regioselectivity in the presence of tiny amounts of the polymeric sulphides, usually in solvent-free conditions (unless the phenol starting material is solid at temperatures even above about 50 °C). Notably, poly(alkylene sulphide)s containing longer spacer groups are particularly para-selective in the chlorination of m-cresol and m-xylenol, while, ones with shorter spacers are particularly para-selective in the chlorination of phenol, 2-chlorophenol, and o-cresol. Such chlorination processes result in some of the highest para/ortho ratios reported for the chlorination of phenols.

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Section: The Use Of Structured Solids To Influence the Halogenation Reactions Of Aromatic Compoundsmentioning

confidence: 96%

Section: The Use Of Structured Solids To Influence the Halogenation Reactions Of Aromatic Compoundsmentioning

confidence: 99%

Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

Smith

El‐Hiti

2021

Organics

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“…Preparation of novel effective reagents for electrophilic chlorination of aromatic compounds has been described. 91 It was found that many chlorine-containing organic compounds acquire strong electrophilic properties in the presence of silica gel, although they differ substantially in reactivities. The systems based on N,Ndichlorourethane, dichloramine-T and tert-butyl hypochlorite appeared to be the most active.…”

Section: Halogenation Of Aromatic Compoundsmentioning

confidence: 99%

“…The tert-butyl hypochlorite ± chromatographic silica gel (BDH) system proved to be very convenient for monochlorination of some aromatic compounds. 91 In some cases, the yields of ortho-and parachlorinated derivatives reached 100%. This reaction has significant advantages over classical electrophilic chlorination reactions involving chlorine and sulfuryl chloride and is characterised by high yields, ease of isolation of reaction products and the absence of HCl.…”

Section: Halogenation Of Aromatic Compoundsmentioning

confidence: 99%

Silica gel in organic synthesis

2001

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The data on the use of silica gel in organic synthesis are The data on the use of silica gel in organic synthesis are presented. Some specific features of cyclisation (both intra-and presented. Some specific features of cyclisation (both intra-and intermolecular) reactions, rearrangements, reduction, oxidation, intermolecular) reactions, rearrangements, reduction, oxidation, condensation, formylation, hydration and dehydration, protec-condensation, formylation, hydration and dehydration, protection of functional groups, tion of functional groups, etc etc., in the presence of silica gel, are ., in the presence of silica gel, are discussed. The bibliography includes 96 references discussed. The bibliography includes 96 references. .

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“…His interest started from a chance observation during chromatographic purification of chloroalkane products from organoborane reactions with dichloramine-T. 32 Traces of new products generated during chromatography encouraged examination of combinations of silica with various chloro compounds, which proved to be effective electrophilic chlorinating agents for substitution of toluene and other aromatic compounds. 33 Use of a zeolite instead of silica allowed control of the regiochemistry of the reaction, so that greater para-selectivity could be achieved. 34 Keith also examined N-bromosuccinimide in the presence of silica, which turned out to be an excellent selective reagent for bromination of heterocyclic compounds such as indoles, benzimidazoles, carbazoles, β-carbolines and iminodibenzyls.…”

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confidence: 99%

A tribute to Prof. Keith Smith

El‐Hiti¹

2012

Arkivoc

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A male child born in Walsall, England, on January 15 1947 to a family in difficult circumstances was adopted by a miner and his wife from North Staffordshire and his name became Keith Smith. As a result, Keith grew up in the rural village of Brown Edge, close to the pottery city of Stoke-on-Trent. Following the death of his mother when he was five years old, his father re-married and Keith acquired two older step-siblings. He attended the local primary school in Brown Edge, but as one of the fortunate few from the village to pass the "eleven-plus" examination his secondary education was at Leek High School, necessitating a 7 mile each way daily bus trip to Leek. It was during his time at Leek High School that he met his future wife, Lynn, who attended the neighboring high school for girls. It was also there that his interest in science, and in chemistry in particular, was stimulated. When he left Leek High in 1965 he was awarded the Mathematics, Chemistry and University Entrance Prizes.He then attended Manchester University, where he studied Chemistry. He was awarded the A F Edwards Memorial Prize at the end of his first year and went on to achieve a BSc with First Class Honors in 1968. Following his graduation, two of the most significant events that would influence his future life occurred. In August he married Lynn and in October he began research studies under the supervision of Dr Andrew Pelter, then a young member of staff in the Chemistry Department at Manchester University.His initial research project involved continuation of recent work of the Pelter group, which depended upon reactions of acyloxyboron compounds. This was successful and his first paper, on synthesis of thioesters, was submitted just a few months after he started his studies. 1 However, around that time H C Brown's seminal work into the hydroboration reaction had demonstrated that many different organoboron compounds could be easily synthesised and the first useful synthetic reactions of such compounds were beginning to emerge. With

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New Reagent Systems for Electrophilic Chlorination of Aromatic Compounds: Organic Chlorine-Containing Compounds in the Presence of Silica

Cited by 33 publications

References 0 publications

Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

Silica gel in organic synthesis

A tribute to Prof. Keith Smith

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