TETRAHEDRON Pergamon Tetrahedron 54 (1998) 1457-1470 Consecutive Michad-Addition-Olefination Sequences with Cr(CO)3-Complexed Aryi Allenylphosphonates - An Efficient Synthesis of Heterocydic Substituted Arene Complexes Thomas J. J. MUller* and Markus Ansorge lnstitutfur Organische Chemie,Ludwig-Maximilians-Universit~it Mtinchen,Karlstr.23, D-80333 Mtinchen, Germany Dedicated to Prof. Dr. Klaus Hafner on the occasion of his 70th birthday Received 4 November 1997; accepted 19 November 1997 Sununary: The Michael-Addition of 1,2 and 1,3-difunctional carbonylcompounds6 to Cr(CO)3- complexed aryl allenylphosphonates 5 followed by an intramolecular Horner-Emmons- Wadsworth olefinationin boilingTHF gives rise to arene Cr(CO)3 substitutedheterocycles 7 in moderate to good yields. © 1998ElsevierScienceLtd. All rights reserved. INTRODUCTION Among numerous reactions mediated by Cr(CO)3-complexed arenes sidechain functionalizations 1 represent the most intriguing synthetic options. In addition to steric effects of the bulky chromiumcarbonyl tripod Cr(CO) 3 complexation alters the electronic properties of arenes significantly. As a consequence of the net electron withdrawing properties of the chromium carbonyl tripod complexed arenes are able to stabilize benzylic anions very efficiently.lC Remarkably, some nucleophiles can be added to styrene complexes to give stable benzylic carbanions, however, the scope of this useful synthesis is limited only to stabilized carbanions, la'c Since quite a number of nucleophiles are known to react readily with acceptor substituted allenes at the central carbon atom 2'3 we suggest the use of allenyl substituted arene Cr(CO)3-complexes4 which upon nucleophilic addition generate stabilized allyl anions for further functionalization. Furthermore, acceptor substituted allenes are key building blocks in the synthesis of five- and six-membered heterocycles. 3a Recently, we could show that Cr(CO)3-complexed benzylphosphonate anions react in a Homer-Emmons- Wadsworth (HEW) reaction with aldehydes to give alkenyl substituted arene Cr(CO)3-complexes in good yields.5 Thus, complexed aryl allenyl phosphonates could be suitable substrates for Michael addition- olefination sequences giving rise to dienyl, carbo or heterocyclic substituents on arene Cr(CO)3-complexes 0040-4020/981519.00 © 1998 Elsevier Science Ltd. All fights reserved. PH: S0040-4020(97) ! 0381-7