text: Intramolecular Diels–Alder (IMDA) reactions pair tethered dienes and dienophiles in a [4+2] fashion, the most common being terminal substitution. These transformations are popular in total synthesis and have seen a wide spread use in advance to numerous difficult synthetic targets. One such use is the application of an enantioselective IMDA transformation in the asymmetric synthesis of the marine toxin  (10).
  The synthesis of  demonstrated the utility of cationic Cu(II)bis(oxazoline) complex catalyzed IMDA reactions to give bicyclic products with as many as four neighboring stereogenic centers (figure 3). A rather recent application of IMDA reactions in complex molecule synthesis is the IMDA approach to the tricyclic core of palhinine lycopodium alkaloids, a class of natural products isolated from nodding club moss.
  N–heterocyclic carbenes (NHCs) are an emerging class of organocatalysts that are able to induce Umpolung reactivity as well as normal polarity transformations, however until recently these have not been broadly used in total synthesis due to limited substrate scope.   An interesting expansion in the use of these organocatalysts is the NHC catalyzed olefin isomerization/IMDA cascade reaction to give unique bicyclic scaffolds. Dienyl esters such as 11 were transformed into substituted bicyclo[2.2.2]octanes via an isomerization step stabilized by a hemiacetal azolium intermediate (13). The activation barrier of isomerization of 1,3–hexadiene through a [1,5]–shift is 41 Kcal mol–1 and is expected to increase with conjugation to the ester, thus uncatalyzed isomerization is unlikely. This provides the advantage of bypassing a high barrier of activation, providing access to previously unobtainable IMDA derivatives.