NMR and IR spectroscopy and X-ray diffraction were used to show that the reaction of 2,2,2-trichloro-and 2,2,2-tribromo-5-methylbenzo[d] [1,3,2]dioxaphospholes with para-substituted arylacetylenes proceeds with regioselective formation of 4-aryl-2-halo-7-methyl-2-oxobenzo[e][1,2]oxaphosphorines. With the trichlorophosphole, selective chlorination of the phenylene fragment in the para position to the endocyclic oxygen atom occurs. With the tribromophosphole, 6-bromo-and unsubstituted benzo[e][1,2]oxaphosphorines are formed as major products. The molecular and supramolecular structure of some of the obtained oxaphosphorines was studied by X-ray diffraction.We recently showed [2] that the reaction of 2,2,2-trichlorobenzo[d][1,3,2]dioxaphosphole (I) with arylacetylenes unexpectedly provides 4-aryl-2,6-dichlorobenzo[e][1,2l 5 ]oxaphosphorine 2-oxides. This mechanistically rather complex reaction involves facile formation of the phosphoryl group and carbon3phos-phorus bond, ipso substitution of the oxygen atom, and regioselective chlorination of the phenylene substituent in the para position to the oxygen atom of the foming benzo[e][1,2]oxaphosphorine ring. Introduction of one, two, or four halogen atoms in the ophenylene fragment of starting phosphole I does not alter the reaction pathway [335], but the regioselective chlorination of the benzo fragment to form 4-aryl-2,6,7-trihalobenzo[e][1,2]oxaphosphorines takes place only if it bears only one halogen substituent.In this work we present the results of investigation of the effect of the electron-donor methyl substituent in the phenylene fragment of 2,2,2-trichloro-and 2,2,2-tribromo-5-methylbenzo[d][1,3,2]dioxophospholes (II, III) on the synthetic result of their reaction with arylacetylenes. It was found that the reaction of compound II with arylacetylenes proceeds with a high degree of regioselectivity and leads mainly (or exclu-ÄÄÄÄÄÄÄÄÄÄÄÄ 1 For communication V, see [1].
