Selective electrophilic cyclization of -carbonylarylacetylenols for the synthesis of cyclopenta[]naphthalenol and 2-phenylnaphthalen-1-ol analogs

• Published in: Organic & biomolecular chemistry Vol. 21; no. 42; pp. 85 - 8515
• Main Authors: Jantrapirom, Jantra, Yongpanich, Phornphan, Tummatorn, Jumreang, Chainok, Kittipong, Jiajaroen, Suwadee, Thongsornkleeb, Charnsak, Ruchirawat, Somsak
• Format: Journal Article
• Published: 01.11.2023
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/d3ob01344h

This work demonstrates a new method for the synthesis of cyclopenta[ a ]naphthalenol and 2-phenylnaphthalen-1-ol analogs via selective cyclization. ortho -Alkynylarylkenones were employed as the common substrates that could be prepared by Sonogashira coupling between 2-haloarylacetophenone and pent-4-yn-1-ol derivatives. These precursors were used without purification to construct 2-phenylnaphthalen-1-ol intermediates by treating with (+)-CSA under heating conditions. Selective cyclization occurred when the reaction was conducted in methyl trimethylacetate solvent which predominantly produced the 2-phenylnaphthalen-1-ol product through 6- endo-dig cyclization without elimination or the formation of cyclopenta[ a ]naphthalenol via shutting down the 5- exo-dig mode of cyclization. Switching the acid from a Brønsted acid to Bi(OTf) 3 led to smooth reactions, providing the cyclopenta[ a ]naphthalenol products in moderate to good yields. Moreover, we also demonstrated the utilization of 2-phenylnaphthalen-1-ol to prepare naphthoquinone, which is an important core structure of bioactive and natural product compounds. Synthesis of cyclopenta[ a ]naphthalenols and 2-phenylnaphthalen-1-ols via selective electrophilic cyclization using o- carbonylarylacetylenols is reported. Selectivity can be controlled using different acids and solvents to give a variety of products.