Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 8. Preparation of symmetrical and unsymmetrical 1,3-diynes from alkynoyl ylides and oxalyl diylides
摘要:
Seven examples of the alkynoyl phosphorus ylides 5 have been prepared and are found, upon flash vacuum pyrolysis (FVP) at 750 degrees C, to undergo extrusion of Ph(3)PO to give the unsymmetrical 1,3-diynes 9 in moderate yield. Six examples of the oxalyl diylides 6 have been prepared and their fully assigned C-13 NMR spectra are presented. Upon FVP, those with R = aryl undergo two-fold extrusion of Ph(3)PO to give symmetrical 1,3-diynes 13 but this requires the unusually severe temperature of 900 degrees C. In contrast those with R = CO(2)Me, CO(2)Et or COPh undergo complete reaction at 500 degrees C but afford only Ph(3)PO and fragmentation products.
The reaction of the stabilisedylides 14–23 with an excess of NO2 in CH2Cl2 at room temperature gives different results depending on the structure of the starting ylide. The monacyl ylides 14–16 give the corresponding α-oxo nitriles 4 together with Ph3PO · HNO3 (24) which has been fully characterised for the first time. Under the same conditions, the ylide 18 gives 2,4-dinitrobenzonitrile (26), Ph3PO
Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 8. Preparation of symmetrical and unsymmetrical 1,3-diynes from alkynoyl ylides and oxalyl diylides
作者:R. Alan Aitken、Hugues Hérion、Caroline E. R. Horsburgh、Nazira Karodia、Shirley Seth
DOI:10.1039/p19960000485
日期:——
Seven examples of the alkynoyl phosphorus ylides 5 have been prepared and are found, upon flash vacuum pyrolysis (FVP) at 750 degrees C, to undergo extrusion of Ph(3)PO to give the unsymmetrical 1,3-diynes 9 in moderate yield. Six examples of the oxalyl diylides 6 have been prepared and their fully assigned C-13 NMR spectra are presented. Upon FVP, those with R = aryl undergo two-fold extrusion of Ph(3)PO to give symmetrical 1,3-diynes 13 but this requires the unusually severe temperature of 900 degrees C. In contrast those with R = CO(2)Me, CO(2)Et or COPh undergo complete reaction at 500 degrees C but afford only Ph(3)PO and fragmentation products.