Cyclic Aminophosphites and -phosphoranes Possessing Six- and Higher-Membered Rings: A Comparative Study of Structure and Reactivity

Aminophosphoranes 2 and 4−9
with a cyclohexylamino substituent and ring sizes varying from five to
eight
have been synthesized by oxidative addition reactions of cyclic
aminophosphites with diols or 1,2-diketones.
The reactivities of these phosphoranes are compared with those of
the corresponding cyclic aminophosphites.
The difference in hydrolytic pathways between amino- and analogous
phenoxyphosphoranes is discussed. X-ray
structures of two sets of compounds, (a)
(C6H11NH)P(OCH2CMe2CH2O)
(1) and
(C6H11NH)P(OCH2CMe2CH2O)(1,2-O2C6Cl4)
(2) and (b)
(C6H11NH)P{O-(t-Bu)2C6H2)2CH2}
(3) and
(C6H11NH)P{(O-(t-Bu)2C6H2)2CH2}(1,2-O2C6H4)·1/2Et2O
(4·1/2Et2O) have
been determined and geometrical parameters compared between
the
P(III) and the corresponding P(V) compounds. In 1, the
six-membered ring has a chair conformation with the
amino group axial; in 2, the six-membered ring is located
apical-equatorial in a trigonal bipyramidal geometry
and has a boat conformation. The eight-membered ring has a
boat-chair conformation in 3, whereas the same
ring has a tub conformation in 4.