Nucleophillic Additions to Carbonyl and Imine Compounds

Dunach and coworkers have reported an unconventional method to access thiolactones. In their work, BF3 OEt2 efficiently catalyzes the isomerization of thionolactones (68) to the corresponding thiolactones (69). This process is quite general in substrate scope and gives the requisite products in good yields (Equation 43) 

They also found that this form of isomerization is stereospecific. Using optically pure (R)-y-thionodecalactone (70) in the presence of 10 mol% of BF3 OEt2 led to the formation of (S)-y-thiodecalactone (71) with complete inversion of configuration at the stereogenic center (Equation 44) [43].  

Boron Lewis acids have been employed routinely to activate carbonyl and imine functionalities toward nucleophillic attack. This section describes examples of achiral and chiral Mukaiyama-aldol reactions as well as carbonyl addition chemistry that require activation with boron Lewis acids. 

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