Unexpected formation of a novel macrocyclic tetraphosphine: (RSSR)-1,9-dibenzyl-3,7,11,15-tetramesityl-1,9-diaza-3,7,11,15-tetraphosphacyclohexadecane

Abstract

The title compound was synthesised in moderate yield via stereoselective self-assembly of two bisphosphine, four formaldehyde and two primary amine molecules.

Synthesis of New Examples of Corands with 16-Membered P,N-Containing Core Ring

“…In the NMR spectra of freshly dissolved compounds 6-14 only one set of signals attributed to one stereoisomer was observed. Signals of core ring protons were similar for all obtained macrocycles and resembled the picture characteristic for corands 1-4, [15,16] including unusual high-field shifted H A signal of P-CH A -N fragment at 2.66-2.83 ppm (3.2-3.6 ppm is an ordinary value of chemical shifts of high-field signal of P-CH 2 -N cyclic fragments). The last observation could be regarded as a characteristic of a macrocycle formation.…”

“…The NMR monitoring of the reaction mixtures showed that the reactions proceeded with the formation of plenty of intermediates and the reaction mixtures were enriched by the isolated products only at the final stage, as in the case of macrocyclizations described above. [14][15][16] Thus, we have again met the phenomenon of the covalent self-assembly.…”

“…[13][14][15][16] Because the last diphosphine with mesityl groups on phosphorus atoms is noticeably more stable to air oxidation and smells less repulsive we have used it as a starting compound for the developing of the self-assembly approach to the 16-membered P,N-containing macrocycles.…”

“…1,3-Bis(mesitylphosphino)propane [15,19] was obtained according to the described method. All manipulations with the secondary phosphine and solutions of macrocycles were carried out by standard high-vacuum and dry-nitrogen techniques in dry degassed solvents which were purified by standard methods.…”

“…[13,14] The Mannichtype condensation of primary and secondary phosphines as proton-donating reagents has been chosen as the basic reaction for the use of covalent self-assembly approach in the synthesis of P,N-containing macrocycles. Recently few examples of the new type of 16-membered P,Ncontaining macrocycles 1-4 namely 1,9-diaza-3,7,11,15-tetraphosphacyclohexadecanes [13][14][15][16] and first cryptand 5 with the same core ring [13,17] (Scheme 1) have been described. However, as it has been mentioned in the review of C.D.…”