99668-30-1Relevant articles and documents
The Nature of Cationic Intermediates Derived from α-Thiophosphoryl and α-Thiocarbonyl Mesylates. Neighboring Thiophosphoryl and Thiocarbonyl Participation
Creary, Xavier,Mehrsheikh-Mohammadi, M. E.
, p. 7 - 15 (2007/10/02)
A series of mesylate derivatives of α-hydroxy thiophosphonathes, RCH(OMs)PS(OEt)2 (8), have been prepared.These mesylates can react by kc processes under solvolytic conditions if cation stabilizing groups such as p-anisyl or p-thioanisyl groups are present.However, under conditions of appropriate electron demand, mesylates 8 can react by kΔ processes involving thiophosphoryl participation.The cyclic intermediate ions capture acetic acid at phosphorus and lead ultimately to α-thio acetate derivatives of phosphonates.This overall transformation converts the P=S function to the P=O group.Rates of acetolyses of 8 can exceed those of the O-phosphoryl analogues by large factors when kΔ processes are involved (as expected for anchimerically assisted processes).Mesylate derivatives of α-hydroxy thio esters, R2C(OMs)CSOCH3 (9), can also react by kΔ processes as shown by enhanced rates relative to simple ester analogues.The substrate (R)-(-)-PhCH(OMs)CSOCH3 (38) gives an acetolysis product that is largely retained, while 9 (R = Me) gave a large fraction of a rearranged product.These data all argue in favor of neighboring thiocarbonyl participation in 8, giving cyclized intermediate cations.The behavior of mesylates 8 and 9 can therefore be quite different from that of the corresponding O-phosphoryl and carbonyl analogues.Neighboring group participation in 8 and 9 accounts for the differences.The contrasting behavior of 8 and 9 also argues against neighboring phosphoryl or carbonyl participation in solvolyses of mesylate derivatives of α-hydroxy phosphonates or α-keto mesylates.
