Reaction of (phenylenedioxy)trihalophosphoranes with arylacetylenes: VI. Regiochemistry of the reaction of 2,2,2-trihalo-5-methylbenzo[d][1,3,2]dioxaphospholes with arylacetylenes

Abstract

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].

Reaction of Trihalo(phenylenedioxy)phosphoranes with Arylacetylenes: VII. Regiochemistry of Reaction 2,2,2-Tribromo-5-halobenzo[d]-[1,3,2λ5]dioxaphospholes with Arylacetylenes

“…In the 31 P NMR spectrum, the product gives a signal at d P 5.8 ppm ( 2 J PCH 27.0 Hz) and in the 1 1 Hz, whose values are close to those in compounds V and VI [2]. The spectrum contains six more signals belonging to carbon atoms directly coupled with protons, and five signals of carbon atoms not involved into such interaction.…”

“…These spectral data correspond to product XIa which contains no ÄÄÄÄÄÄÄÄÄÄÄÄ bromine in the phenylene fragment. The fact that the signal of C 7 is downfield (d 137.72 ppm) from that of C 6 (d 130.41 ppm) [1] suggests that chlorine locates in the 7 position of benzophosphinine XIa. Analogously, compounds XIb and XIc are preferentially formed from 5-chlorophosphole Xa and p-tolylacetylene, as well as from 5-bromophosphole Xb [prepared from phosphorobromidite IXb] and phenylacetylene.…”

“…Unlike tribromophospholes Xa and Xb, 2,2-dibromo-5-chloro-2-fluorobenzo[d] [1,3,2]dioxaphosphole (XVI) prepared from P(III) derivative XV reacts with phenyl-and p-tolylacetylene in a more complicated manner to give three benzophosphinines are formed, whose ratio slightly varies, depending on the concentration of the starting reagents. In any case, one of the products is preferred (53360%).…”

“…We recently showed that the reactions of a readily available P(V) halide, 2,2,2-trichlorobenzo[d] [1,3,2l 5 ]-dioxaphosphole (I), with arylacetylenes or propargyl chloride give benzo[e] [1,2]oxaphosphinines II and III. The reactions occur in mild conditions and involve formation of a phosphorus3carbon bond and phosphoryl group, as well as ipso-substitution of oxygen by carbon in the benzene ring.…”

“…Depending on the nature of the alkyne, chlorine is regioselectively introduced para (with phenylacetylene) or ortho (with propargyl chloride) to the oxygen atom of the phosphinine ring [2,3]. 5 ]dioxaphosphole (IV) reacts with arylacetylenes to form benzophosphinines V and VI, the latter having no bromine in the benzene ring [1]. If starting trichlorobenzophosphole VII contains a 5-Br substituent, chlorine is introduced in the preferentially formed benzophosphinine occurs so that both halogens are ortho to each other and para to the fused phosphinine ring [4].…”