Strategy for employing unstabilized nucleophiles in palladium-catalyzed asymmetric allylic alkylations.
We report a strategy for the employment of highly unstabilized anions in palladium-catalyzed asymmetric allylic alkylations (AAA). The "hard" 2-methylpyridyl nucleophiles studied are first reacted in situ with BF3.OEt2; subsequent deprotonation of the resulting complexes with LiHMDS affords "soft" anions that are competent nucleophiles in AAA reactions. The reaction is selective for the 2-position of methylpyridines and tolerates bulky aryl and alkyl substitution at the 3-, 4-, and 5-positions. Investigations into the reaction mechanism demonstrate that the configuration of the allylic stereocenter is retained, consistent with the canonical outer sphere mechanism invoked for palladium-catalyzed allylic substitution processes of stabilized anions.
Trost
Barry M
BM
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA. bmtrost@stanford.edu
Thaisrivongs
David A
DA
D000478:Alkylation; D000498:Allyl Compounds / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000498:Allyl Compounds; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D010165:Palladium