A Facile Synthesis of Carbamoylsilanes, -boranes and -phosphane Oxides - Isolation of the First Uncomplexed Carbamoylborane.

C-(Trimethylsilyloxy)-, C-(triisopropylsilyloxy)-, C-(diphenylboryloxy), C-[bis(diisopropylamino)boryloxy]- and C-(di-tert-butylphosphoryloxy)-N,N-diisopropylaldiminium salts are readily prepared in good to excellent yields from either diisopropylformamide or (chloromethylene)diisopropylammonium chloride. Deprotonation of these aldiminium salts leads to transient (amino)(oxy)carbenes, which cleanly rearrange to carbamoyl derivatives. This synthetic methodology gives access to sterically hindered carbamoylsilanes, -boranes and phosphane oxides that are hardly accessible by other routes.