Synthesis of indoles via 6pi-electrocyclic ring closures of trienecarbamates.
A new method for the preparation of indoles from readily available alpha-haloenones and alpha-(trialkylstannyl)enecarbamates is described. Following a Stille coupling, trienecarbamate 2 is electronically activated to undergo a facile 6pi-electrocyclic ring closure and subsequent oxidation to afford protected aniline 4. Upon deprotection and reductive amination, acid 5 underwent clean cyclization to N-acetylindole 6 (Ac2O, NEt3, 130 degrees C). This method has been used to construct a variety of substituted indoles that are not easily prepared by conventional indole annelation methods.
Greshock
Thomas J
TJ
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Funk
Raymond L
RL
D002219:Carbamates / Q000737:chemistry*; D003500:Cyclization; D007211:Indoles / Q000138:chemical synthesis*; D011090:Polyenes / Q000737:chemistry*
D002219:Carbamates; D007211:Indoles; D011090:Polyenes