A set of coumarin-fused electron-deficient 1,3-dienes was synthesized, which differ in the nature of the electron-withdrawing group (EWG) at the terminus of the diene unit and (when EWG = CO(2)Me) the nature and position of substituents. These dienes reacted with the enamine derived from cyclopentanone and pyrrolidine to afford the corresponding cyclopenteno-fused 6H-dibenzo[b,d]pyran-6-ones, most likely via a domino inverse electron demand Diels-Alder (IEDDA)/elimination/transfer hydrogenation sequence. The parent diene (EWG = CO(2)Me, no substituents) was reacted with a range of electron-rich dienophiles (mostly enamines) to afford the corresponding 6H-dibenzo[b,d]pyran-6-ones or their nondehydrogenated precursors, which were aromatized upon treatment with a suitable oxidant. The enamines could either be synthesized prior to the reaction or generated in situ. The syntheses of 30 dibenzopyranones are reported.

A multicomponent domino reaction that affords 6H-dibenzo[b,d]pyran-6-ones is reported. The overall transformation consists of six reactions: Knoevenagel condensation, transesterification, enamine formation, an inverse electron demand Diels-Alder (IEDDA) reaction, 1,2-elimination, and transfer hydrogenation. Both the diene and dienophile for the key inverse electron demand Diels-Alder (IEDDA) step are generated in situ by secondary amine-mediated processes. In most cases, the yields (10-79%) are considerably better than those obtained using a stepwise process. This methodology is employed in a concise total synthesis of cannabinol.

A survey of olefination reactions that have been used in the synthesis of cyclophanes is presented. This covers the Ramberg-Bäcklund reaction, the Wittig and related reactions, the McMurry and related reactions, ring-closing metathesis (alkenes, alkynes and ene-ynes), aldol condensations and Siegrist reactions, as well as miscellaneous reactions. The McMurry reaction and ring-closing metathesis have enjoyed the greatest popularity in recent years, but they are typically used for complementary purposes. In virtually all cases, the McMurry reaction is used to install a twocarbon (1,2-ethenylene) bridge, whereas ring-closing metathesis is used to construct bridges that are at least fourmembered, but usually considerably longer. Some wellknown olefinations have seen little or no use in the field of cyclophane chemistry.The Ramberg-Bäcklund reaction [9] is the final step in a two-to three-step thioether-to-alkene conversion. As such, it appears to be well-suited for the synthesis of alkene-containing cyclophanes. Even though it applies to pre-existing cyclophanes, it warrants attention in the context of this review because both bonds of the newly formed alkene are generated during the reaction. Within the broader scope of organic synthesis, the Ramberg-Bäcklund reaction has been exploited frequently to introduce a double bond into large rings, [10] small rings [11] and more exotic ring systems such as cyclic enediynes. [12] However, it has not performed well in the synthesis of cyclophanes.The first cyclophanes to be synthesized using the Ramberg-Bäcklund reaction were the isomeric biphenylophanes (Z,Z)-7 and (E,E)-7 (Scheme 3). [13] As expected from mechanistic considerations, [14] they were formed stereospecifically in good yield (both 65 %) from the diastereomeric sulfones meso-6 and (AE)-6, respectively. Interestingly, the report of these very good results came shortly after Boekelheide wrote that "the Ramberg-Bäcklund reaction is unsatisfactory when applied to 2,11-dithia-[3.3]cyclophanes". [15] Prior to Boekelheides comment on the Ramberg-Bäcklund reaction, Martel reported that a Ramberg-Prof. Graham Bodwell obtained his B.Sc. and M.Sc. from the University of Victoria, Canada, working with Prof. Reginald Mitchell on cyclophanes. He then moved to Braunschweig, Germany, where he joined the group of Prof. Dr. Henning Hopf as a "Doktorand". Cyclophanes were also the focus of his doctoral research. He then took a break from cyclophanes and worked in the field of asymmetric synthesis as a post-doctoral fellow with Prof. Steve Davies at Oxford University. He then accepted a faculty position at Memorial University, where he now holds the rank of Professor. Cyclophanes have always been one of his core research interests.Penchal Reddy Nandaluru obtained his B.Sc. and M.Sc. from Sri Venkateswara University, India, and then worked as a chemist with AVRA Laboratories in India before joining the group of Prof. Graham Bodwell at Memorial University in St. John's, NL, Canada. The main theme of his doctoral research is the appli...

A very short synthesis (5 steps), the crystal structure and resolution of an elaborate, inherently chiral [n](1,6)pyrenophane is reported. The synthesis hinges upon two very productive events: a multicomponent reaction and an unprecedented double-McMurry/valence isomerization/dehydrogenation step. Aromatization reactions are involved in the formation of all four of the rings of the pyrene system.

A concise total synthesis of defucogilvocarcin V is reported. The key features of the approach are the formation of the C-ring using a vinylogous Knoevenagel/transesterification reaction and construction of the D-ring by way of an inverse electron demand Diels-Alder-driven domino reaction. The resulting C-8 ester functionality provides a handle for the synthesis of defucogilvocarcin V as well as some C-8 analogues from a common late-stage intermediate.