Dipolarophiles fulvenes

A further illustration of the electronic influence of substituents on the course of reactions with 1,3-dipoles can be seen in the cycloaddition of an amino-substituted fulvene to benzonitrile oxide. Adduct (76) was obtained in 60% yield when the electron-rich dipolarophile 6-dimethylaminofulvene was exposed to benzonitrile oxide. The structure of the resultant product can be conveniently explained by an initial [6... 

Muthusamy and co-workers have demonstrated [82] the reactions of the bicyclic ylide 57, generated from the diazocarbonyl compoimd 56, with symmetrical and unsymmetrical dipolarophiles. Thus, exposure of the cyclohexanone-substituted a-diazocarbonyl compound 56 to DMAD in the presence of Rh2(OAc)4 as the catalyst has furnished the cycloadduct 58 (Scheme 16). This cycloaddition was diastereoselective and, in the case of unsymmetrical dipolarophiles such as methyl methacrylate and propargyl bromide, they were regioselective and afforded oxygen heterocycles 59 and 60, respectively. The same research group has reported the 1,3-dipolar cycloaddition of the bicyclic carbonyl yUde 57 with other dipolarophiles, namely fulvenes [83]. In these tandem cycUzation-cycloaddition reactions involving fulvenes, four stereocenters and two new C-C bonds are formed in a single step. Symmetrical dipolarophiles such as macrocycHc olefins were also used for diastereoselective 1,3-dipolar cycloaddition reaction with 56 [84]. 

Other reactive olefins, such as enamines and vinyl ethers also participate as dipolarophiles in their reaction with thiocarbonyl 5-imides. Even fulvenes undergo [3+2] cycloaddition reactions. 

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