The Preparation of Some Heterocyclic Analogues of Triptycene

Abstract

A variety of anthracenes react with dibenzoylethylene and diacetylethylene to give substituted bicyclooctadienes as Diels–Alder adducts. Treatment of these with phosphorus pentasulfide gives derivatives of benzenonaphtho[c]thiophenes, which are thiophene analogues of triptycene. Reaction of the anthracenes with dibenzoylacetylene gave substituted bicyclooctatrienes, which on treatment with phosphorus pentasulfide gave inseparable mixtures of the benzenonaphtho[c]thiophenes and benzenonaphtho[c]-furans. Attempted retro Diels–Alder reactions of the thiophenes were unsuccessful.

Gain or loss of aromaticity in Diels–Alder transition states and adducts: a theoretical investigation

“…In QDM, there are two diene units, one endocyclic and the other exocyclic, and theoretically both units can take part in the Diels-Alder reaction. However, the exocyclic diene unit is known to react preferably over the other 6 and it can also be verified from the frontier orbitals of QDM that the exocyclic diene unit forms the HOMO. Similarly in ANT, 7 although different diene units are available for the reaction, it is the diene in the central ring that is the most active; 5 HOMO vectors also predict the same.…”

“…QDM is a highly reactive diene and is usually generated 6 in situ from thermal ring opening of benzocyclobutane. In QDM, there are two diene units, one endocyclic and the other exocyclic, and theoretically both units can take part in the Diels-Alder reaction.…”

“…In VN, both experimental observations 8 and HOMO vectors show that the ring innerouter diene is the most active in Diels-Alder reactions. Experimental reports [5][6][7][8] suggest that, of these three reactions, the QDM reaction is considerably faster and the other two are relatively slow. Of ANT and VN, the latter is found to react less readily than the former in Diels-Alder reactions.…”

“…We selected a set of three simple masked dienes, viz. oquinodimethane (QDM), 5,6 anthracene (ANT) 5,7 and avinylnapthalene (VN), 5,8 which are ring-fused dienes, and reacted them with ethylene to investigate factors that control the reactions. In addition to the above, the reactions of VN with maleic anhydride (MA) and pbenzoquinone (BQ) were also studied to observe the most preferred stereoselective TS in the reaction.…”

“…A common factor in these dienes is the gain or loss aromaticity by the remaining part of the molecule when the diene reacts. The reactions selected for the investigation here have been thoroughly studied experimentally [5][6][7][8] and the relative reactivities of the above dienes are known.…”