A set of 1,3,2-oxazaphosphorino[4,3-a]isoquinolines 6a,b-9a,b, a new ring system, was synthesized, and their stereochemical and conformational analyses were performed by 1H, 13C, and 31P NMR methods. X-ray measurements were also carried out to confirm the stereochemical assignments and conformational results obtained by means of NMR. Intermediate coupling constants 3J(P,H) were found for compounds 7 and 9; these do not relate to equilibria between previously reported conformers, but are indicative of new distorted conformational states in solution. The connecting isoquinoline and the steric interaction between the aromatic moiety and the Me-1 substituent can block the oxazaphosphorinane ring. The conformational behavior of compounds 6 and 8 was characterized by the usual chair-twist equilibrium.
ASJC Scopus subject areas
- Organic Chemistry