The use of polymeric sulfides as catalysts for the para-regioselective chlorination of phenol and 2-chlorophenol

ABSTRACT

Various poly(alkylene sulfide)s have been synthesized and used as catalysts to enhance the para-regioselectivity in chlorination of phenol and 2-chlorophenol using freshly distilled sulfuryl chloride in the presence of AlCl₃ as an activator. Poly(alkylene sulfide)s having alternating spacers, one having three methylene groups and the second having three, six or nine methylene groups were the most para-regioselective catalysts in chlorination of both phenol and 2-chlorophenol. For example, chlorination of phenol and 2-chlorophenol in the presence of optimal examples of such poly(alkylene sulfide)s gave 4-chlorophenol and 2,4-dichlorophenol as the major products in 94.8 and 95.4% yields, respectively, compared with 75.4 and 55.0% yields in the absence of catalysts. In addition, double chlorination of phenol in the presence of poly(alkylene sulfide)s gave 2,4-dichlrophenol in up to 97.1% yield compared with only 58.6% in the absence of catalysts.

GRAPHICAL ABSTRACT

KEYWORDS:

• Para-regioselective chlorination
• catalysts
• aluminum chloride
• 2,4-dichlorophenol
• phenol
• poly(alkylene sulfide)s

Acknowledgements

A. S. Hegazy thanks Swansea and Cardiff Universities for financial support. G. A. El-Hiti is grateful to the Deanship of Scientific Research, King Saud University for funding through Vice Deanship of Scientific Research Chairs.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Keith Smith http://orcid.org/0000-0003-4838-5651

Gamal A. El-Hiti http://orcid.org/0000-0001-6675-3126

Additional information

Funding

This work was supported by Cardiff University; King Saud University [Grant Number Research Chairs]; Swansea University.