Beiträge zur Chemie des Bors, 219. (Di‐tert‐butylphosphanylimino)(2,2,6,6‐tetramethylpiperidino)boran: ein BNP‐1,3‐”︁Dipol”

Contributions to the Chemistry of Boron, 219[1]. – (Di-tert-butylphosphanylimino)(2,2,6,6,-tetrametylpiperidino)borane: a BNP 1,3-„Dipole” In contrast to amino-imino-boranes R2N–BN–R', which are susceptible to [2 + 2] cycloadditions, the amino(phosphanyl-imino)borane 2 [R = P(tBu)2] performs [3 + 2] cycloadditions with heteroallenes XCY or nitriles to yield the novel five-membered heterocycles 3a–g, 6, 7, and 8. The reactions of 2 are dominated by the phosphorus atom as the nucleophile attacking the carbon atom in XCY and R–CN, respectively. The driving force for the formation of the new heterocycles is obviously provided by the formation of an iminophosphorane structure and a three-coordinated environment at the boron atom. The X-ray-structures of 3a, 3c, 3e, and 3g demonstrate planer heterocyclic rings.