Rhodium-catalysed tetradehydro-Diels-Alder reactions of enediynes a rhodium-stabilized cyclic allene

• Published in: Chemical science (Cambridge) Vol. 11; no. 4; pp. 1945 - 195
• Main Authors: Thadkapally, Srinivas, Farshadfar, Kaveh, Drew, Melanie A, Richardson, Christopher, Ariafard, Alireza, Pyne, Stephen G, Hyland, Christopher J. T
• Format: Journal Article
• Language: English
• Published: 21-10-2020
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d0sc04390g

Efficient methods for the synthesis of fused-aromatic rings is a critical endeavour in the creation of new pharmaceuticals and materials. A direct method for preparing these systems is the tetradehydro-Diels-Alder reaction, however this is limited by the need for harsh reaction conditions. A potential, but underdeveloped, route to these systems is
via
transition metal-catalysed cycloaromatisation of ene-diynes. Herein, tethered unconjugated enediynes have been shown to undergo a facile room-temperature Rh
I
-catalysed intramolecular tetradehydro-Diels-Alder reaction to produce highly substituted isobenzofurans, isoindolines and an indane. Furthermore, experimental and computational studies suggest a novel mechanism involving an unprecedented and complex Rh
I
/Rh
III
/Rh
I
/Rh
III
redox cycle involving the formation of an unusual strained 7-membered rhodacyclic allene intermediate and a Rh
III
-stabilized 6-membered ring allene complex.
Room temperature Rh-catalysed tetradehydro-Diels-Alder reaction
via
an unusual Rh-stabilised allene.