| Abstract: | The reactivity of N‐heterocyclic carbenes (NHCs) and cyclic alkyl amino carbenes (cAACs) with arylboronate esters is reported. The reaction with NHCs leads to the reversible formation of thermally stable Lewis acid/base adducts Ar‐B(OR)2?NHC ( Add1 – Add6 ). Addition of cAACMe to the catecholboronate esters 4‐R‐C6H4‐Bcat (R=Me, OMe) also afforded the adducts 4‐R‐C6H4Bcat?cAACMe ( Add7 , R=Me and Add8 , R=OMe), which react further at room temperature to give the cAACMe ring‐expanded products RER1 and RER2 . The boronate esters Ar‐B(OR)2 of pinacol, neopentylglycol, and ethyleneglycol react with cAAC at RT via reversible B?C oxidative addition to the carbene carbon atom to afford cAACMe(B{OR}2)(Ar) ( BCA1 – BCA6 ). NMR studies of cAACMe(Bneop)(4‐Me‐C6H4) ( BCA4 ) demonstrate the reversible nature of this oxidative addition process. |
