Abstract
AbstractEnantioselective nickel‐catalyzed arylative cyclizations of substrates containing a Z‐allylic phosphate tethered to an alkyne are described. These reactions give multisubstituted chiral aza‐ and carbocycles, and are initiated by the addition of an arylboronic acid to the alkyne, followed by cyclization of the resulting alkenylnickel species onto the allylic phosphate. The reversible E/Z isomerization of the alkenylnickel species is essential for the success of the reactions.
Highlights
Enantioselective nickel-catalyzed arylative cyclizations of substrates containing a Z-allylic phosphate tethered to an alkyne are described
Enantioselective metal-catalyzed allylic substitutions of achiral or racemic substrates using carbon-centered nucleophiles are a major class of reactions for preparing enantioenriched chiral compounds.[1]
Chiral iridium[2g] and rhodium[2i] catalysts are effective in enantioselective additions of alkenylboron reagents to racemic allylic alcohols[2g] and allylic halides,[2i] respectively
Summary
Enantioselective nickel-catalyzed arylative cyclizations of substrates containing a Z-allylic phosphate tethered to an alkyne are described. We describe highly enantioselective intramolecular alkenylations of allylic phosphates with fully substituted alkenylnickel species, which are themselves generated by the nickel-catalyzed addition of arylboronic acids to internal alkynes (Scheme 1 B). The scope of this reaction with respect to the alkynetethered allylic phosphate was explored in reactions with PhB(OH)2, which gave products 2 a–2 i in 45–92 % yield and 49–99 % ee (Scheme 2).
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