Assembly of 5H-dibenzo[a,d]cycloheptenes by a formal [5 + 2] annulation of ortho-aryl alkynyl benzyl alcohols with arenes

Abstract

A new synthetic methodology for the synthesis of 5H-dibenzo[a,d]cycloheptenes from ortho-aryl alkynyl benzyl alcohols and arenes via a Tf2O-mediated formal [5+2] annulation reaction, has been achieved. From this transformation, structurally...

ortho-Alkynyl Benzyl Alcohols as C6 Synthons in Regioselective Construction of Polysubstituted Naphthalenes

“…A plausible mechanism was proposed (Scheme ) based on the control experiments and the previous reports , by using substrate 1a as an example. Initially, ortho -alkynyl benzyl alcohols 1a in situ generate ortho -alkynyl benzyl triflate I along with the release of H 2 O in the presence of Tf 2 O.…”

“…As illustrated in Scheme , they have been used as C2, C4, as well as C5 synthons for [2+ n ], [4+ n ], and [5+ n ] cycloaddition reactions, respectively, to construct highly functionalized polycyclic and heterocyclic compounds (Scheme ). − However, to the best of our knowledge, using ortho -alkynyl benzyl alcohols as C6 synthons to access polysubstituted naphthalenes is seriously limited, especially under metal-free conditions. The main challenge may be attributed to the nucleophilic nature of the hydroxyl group at the benzyl position, which readily undergoes addition reactions with electrophilic groups to give oxygen-containing heterocyclic compounds (Scheme , path a and b). − …”

“…During our previous work on the synthesis of 5 H -dibenzo[ a,d ]cycloheptenes, we found that various 1°- and 2°-substituted ortho -alkynyl benzyl alcohols could be used as C5 synthons to react with p -xylene (as a C2 synthon) via a formal [5+2] annulation reaction (Scheme a). Inspired by these results, we wished to extend this method to 3°-substituted ortho -alkynyl benzyl alcohol 1a .…”

“…13C{ 1 H} NMR (101 MHz, CDCl 3 ) δ 159.1, 141.0, 140 5,. 138.1, 134.2, 133.1, 131.2, 131.1, 128.9, 128.6, 127.5, 127.4, 126.7, 126.2, 126.0, 125.9, 125.1, 113.8, 55.4.…”