The synthesis of a second-generation cobalt catalyst for the formation of trans-THF products via the Mukaiyama aerobic oxidative cyclization is reported. Two procedures have been developed with the new water-soluble catalyst that give superior yields and greatly simplify purification compared to the previous catalysts.

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Rhodium-catalyzed ring-opening reactions of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with arylboronic acids were investigated. The use of [RhCl(COD)](2), (+/-)-BINAP, and NaHCO(3) in MeOH at 60 degrees C was found to be the optimized conditions for the ring-opening reactions to give the 1,2-ring-opened products. Various arylboronic acids were examined, and low to moderate yields were obtained and stereoselectivities (trans/cis) from 50:50 to 100:0 were observed.

Ruthenium-catalyzed nucleophilic ring-opening reactions of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols were investigated. When a neutral ruthenium(II) catalyst, Cp*RuCl(COD), was used in MeOH, the trans-1,2-ring opened product was formed as the only regio- and stereoisomer. On the other hand, when a cationic ruthenium(II) catalyst, [CpRu(CH(3)CN)(3)]PF(6), was used in MeOH, the cis-1,2-ring opened product was formed exclusively. Moderate to excellent stereoselectivity (70:30 to 100:0) was observed with various alcohols.