REVIEW ▌1 Recentreview Progress in the Synthetic Assembly of 2-Cyclopentenones David2-Cyclopentenone J. Synthesis Aitken,*a Hendrik Eijsberg,a,b Angelo Frongia,b Jean Ollivier,a Pier Paolo Pirasb a Laboratoire de Synthèse Organique & Méthodologie, ICMMO (CNRS UMR 8182), Université Paris Sud, 15 rue Georges Clemenceau, 91045 Orsay cedex, France Fax +33(1)69156278; E-mail:
[email protected] b Dipartimento di Scienze Chimiche e Geologiche, Università degli studi di Cagliari, Complesso Universitario di Monserrato, S.S. 554, Bivio per Sestu, 09042 Monserrato, Cagliari, Italy Received: 09.07.2013; Accepted after revision: 21.08.2013 considerable number of ways in which the target ring sys- Abstract: An overview of the most important synthetic strategies currently available for the preparation of cyclopent-2-enones is pre- tem can be created from acyclic precursors, in either inter- sented and illustrated with recent applications. molecular or intramolecular mode. Most of the possible disconnection strategies have been examined, and it is im- 1 Introduction portant to recognize that for any given target 2-cyclopen- 2 Multicomponent Ring Assembly tenone, there may be several convenient approaches 3 Cyclizations available. The main approaches for ring construction are 4 Transformations of Existing Cyclic Systems summarized graphically in Figure 1. 5 Miscellaneous Methods O (4+1) O O (3+2) (3+2) coupling 6 Conclusions 1 1 1 5 5 2 5 2 2 RCM Key words: cyclopentenones, cyclization, carbocycles, ring clo- (4+1) (3+2) Rautenstrauch 4 3 4 3 4 3 aldol-type annulation sure, rearrangement, annulation (2+2+1) PKR Nazarov (3+2) Figure 1 The main ring-construction strategies for 2-cyclopente- none synthesis, showing the atom connectivities made during ring as- 1 Introduction sembly (left and center) and cyclization approaches (right).