Phosphorus-Based Organocatalysis for the Dehydrative Cyclization of -(2-Hydroxyethyl)amides into 2-Oxazolines.

A metal-free, biomimetic catalytic protocol for the cyclization of -(2-hydroxyethyl)amides to the corresponding 2-oxazolines (4,5-dihydrooxazoles), promoted by the 1,3,5,2,4,6-triazatriphosphorine (TAP)-derived organocatalyst tris(-phenylenedioxy)cyclotriphosphazene (TAP-) has been developed. This approach requires less precatalyst compared to the reported relevant systems, with respect to the phosphorus atom (the maximum turnover number (TON) ∼ 30), and exhibits a broader substrate scope and higher functional-group tolerance, providing the functionalized 2-oxazolines with retention of the configuration at the C(4) stereogenic center of the 2-oxazolines. Widely accessible β-amino alcohols can be used in this approach, and the cyclization of -(2-hydroxyethyl)amides provides the desired 2-oxazolines in up to 99% yield.

1,5-Bis[(E)-1-(2-hydroxy-phen-yl)ethyl-idene]carbonohydrazide dimethyl sulfoxide solvate.

The title dimethyl sulfoxide (DMSO) solvate, C(17)H(18)N(4)O(3)·C(2)H(6)OS, shows the disubstituted urea derivative to adopt an almost planar geometry (r.m.s.