ABSTRACT
α-Aminoradicals undergo halogen atom abstraction to form halomethyl radicals in reactions initiated by the combination of tert-butyl hydroperoxide, aliphatic trialkylamine, halocarbon, and copper(I) iodide. The formation of the α-aminoradical circumvents preferential hydrogen atom transfer in favor of halogen atom transfer, thereby releasing the halomethyl radical for addition to alkenes. The resulting radical addition products add the tert-butylperoxy group to form α-peroxy-ß,ß-dichloropropylbenzene products that are convertible to their corresponding ß,ß-dichloro-alcohols and to novel pyridine derivatives. Computational analysis clearly explains the deviation from traditional HAT of chloroform and also establishes formal oxidative addition/reductive elimination as the lowest energy pathway.
ABSTRACT
The cationic alkynyl Heck reaction between aryl triflates and alkynes to give substituted allenes is described. Key to the success of this method was the discovery and development of a new hybrid Pd(0)-catalyst, BobCat, that incorporates a water-soluble dba-ligand and biaryl phosphine ligand to provide substituted allenes in good yields under mild reaction conditions.
Subject(s)
Alkadienes/chemical synthesis , Alkynes/chemistry , Coordination Complexes/chemistry , Mesylates/chemistry , Catalysis , Ligands , Molecular Structure , Palladium/chemistry , Water/chemistryABSTRACT
We wish to report our preliminary results on the discovery and development of a catalytic, asymmetric ß-hydride elimination from vinyl Pd(II)-complexes derived from enol triflates to access chiral allenes. To achieve this, we developed a class of chiral phosphite ligands that demonstrate high enantioselectivity, allow access of either allene enantiomer, and are readily synthesized. The methodology is demonstrated on over 20 substrates, and application to the formal asymmetric total synthesis of the natural product, (+)-epibatidine, is also provided.