Electron transfer initiated cyclization method

Horeancig and co-workers also observed neighboring group participation of acetal ethers in the formation of substituted furanoside in their electron transfer-initiated cationic cyclizations. ° Their efforts have provided a method for oxonium ion generation through the one-electron... 

Similarly, the photosensitized electron transfer mediated reactions of several 1-and 9-(aminoalkyl)phenanthrenes using DCB have been investigated by Lewis and coworkers (Scheme 69) [319], These reactions provide an efficient method of construction of skeletal structures of aporphine, phenanthropiperidine, phenanthroa-zepine and related alkaloids. The mechanism of these reactions involves an initial electron transfer from the ground state amine to the singlet arene followed by N-H proton transfer and biradical cyclization. 

An interesting indole synthesis was realized by Zhao, who reported the PIFA-mediated cyclization of enamines 11 (Scheme 3) [8]. This reaction toward indoles 12 may rely on an electrophilic nitrogen atom to initiate cyclization or proceed through single electron transfer. Related pyrrole derivatives are also accessible by this method. 

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