Synthesis of Polycyclic Ring Systems Using Transition Metal Catalyzed Cyclizations of Diazo Alkynyl Ketones

Abstract

Abstract: The rhodium(II)-catalyzed reaction of α-diazo ketones bearing tethered alkyneunits represents a new and useful method for the construction of a variety of substitutedcyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoidonto the acetylenic π-bond to give a vinyl carbenoid intermediate. The resulting rhodiumcomplex undergoes a wide assortment of reactions including cyclopropanation, 1,2-hydrogen migration, CH-insertion, addition to tethered alkynes and ylide formation. When2-alkynyl-2-diazo-3-oxobutanoates were treated with a Rh(II)-catalyst, furo[3,4- c ]furanswere formed in excellent yield. Keywords: .rhodium, catalyst, diazo, ketone, alkyne, cyclization, CH-insertion, ylide,furo[3,4- c ]furans Introduction The chemistry of transition metal carbene complexes has been a subject of intense activity over thepast two decades [1]. Current interest in this field stems from the role of metal carbenes in alkenemetathesis [2], in alkene and alkyne polymerization [3], in cyclopropanation chemistry [4], and asintermediates in an impressive array of synthetic methodology [5,6]. The intramolecular reactions of