Intramolecular Diastereoselective Cascade Cyclization Reaction of N,N′-Bis(Salicylidene)Cyclohexanediimine with Phosphoryltrichloride to a Bis(Chlorophosphorylated) Decahydro-2,4-DI (2-Hydroxyphenyl)Benzo[d][1,3,6]oxadiazepine

Abstract

A new type of cascade cyclization was observed in the phosphorylation reaction of (R,R)- or (S,S)-N,N′-bis(salicylidene)cyclohexanediimine with phosphoryltrichloride, which resulted in the formation of bis(chlorophosphorylated) decahydro-2,4-di(2-hydroxyphenyl)benzo[d][1,3,6]oxadiazepine with two new stereogenic phosphorus atoms and two new stereogenic carbon atoms in the oxadiazepine ring in the β-position to phosphorus. During the synthesis, the N atom attacks the phosphorodichloridate group with the formation of the P–N bond to give an asymmetric phosphorus atom and an iminium ion. This compound with six stereogenic centers crystallizes in the monoclinic centrosymmetric space group P2₁/c and the crystal structure together with solution and solid-state MAS ¹³C and ³¹P NMR studies reveals a preferential formation of stereoisomers.

GRAPHICAL ABSTRACT

Keywords:

• Cyclization
• chirality
• diastereoselection
• polycyclic phosphorus
• X-ray diffraction

ACKNOWLEDGMENTS

The present work has been supported by the University of Zanjan and by the Fakultät für Chemie und Pharmazie, Ludwig-Maximilians-Universität, Munich. CJ thanks the DFG for grant Ja466/14-1 and Ja466/23-1 (initiation of bilateral cooperation HHM-CJ). We thank Mr. Alfred Hasenhindl from the University of Freiburg for the collection of the solid-state NMR spectra.