Premium
Palladium‐Catalyzed Cascade Oligocyclizations Involving Competing Elementary Steps Such as Thermal [1,5]‐Acyl Shifts
Author(s) -
Tokan Wajdi M.,
Schweizer Stefan,
Thies Claudia,
Meyer Frank. E.,
Parsons Philip J.,
de Meijere Armin
Publication year - 2009
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200900070
Subject(s) - chemistry , palladium , fulvene , medicinal chemistry , cyclohexane , moiety , cycloisomerization , acetylene , catalysis , stereochemistry , organopalladium , hydride , organic chemistry , hydrogen
Palladium(Pd)‐catalyzed oligocyclizations of 2‐bromotetradec‐1‐ene‐7,13‐diynes with an unsubstituted terminal acetylene moiety like 3 and 5 and 15‐bromohexadec‐15‐ene‐3,9‐diyn‐2‐ones like 4 and 6 afforded fulvene derivatives 20 and 21 ( Scheme 7 ) and bis(cyclohexane)‐annulated methylenecyclopentene systems 16 and 18 ( Schemes 5 and 6 ), respectively. These transformations constitute cascades of cyclizing carbopalladation steps with ensuing [1,5]‐sigmatropic H‐atom and acyl shifts, respectively ( Scheme 8 ). In contrast, analogous substrates with one three‐atom and one four‐atom tether between the unsaturated C,C‐bonds, such as 1 and 2 , behave differently in that the Pd‐substituted hexa‐1,3,5‐triene intermediates 12 undergo a 6 π ‐electrocyclization instead of a 5‐ exo‐trig carbopalladation followed by β ‐hydride elimination to furnish tricyclic bis‐annulated benzene derivatives 13 and 14 ( Scheme 4 ).