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. Author manuscript; available in PMC: 2010 Jul 2.
Published in final edited form as: Tetrahedron. 2009 Jun 27;65(26):4957–4967. doi: 10.1016/j.tet.2009.03.103

Scheme 1.

Scheme 1

Initially attempted NHC-catalyzed intramolecular cyclization. (HBTU=O-(benzotriazol-1 -yl)- N,N,N′,N′-tetramethyluronium hexafluorophosphate, DIPEA=N,N-diisopropylethylamine, DBU=1,8-diazabicyclo-[5.4.0]undec-7-ene).