phosphaalkenes with inverse electron density - react primarily at the three-membered ring with nucleophilic reagents. From their reactions with organolithium compounds 2a-c and Grignardreagents 5a,b the cyclopropenylphosphines 4a-f are obtained after addition of chlorotrimethylsilane; of these products only 4a, d, and e were isolated and characterized. Methanolysis of products 4a-f yields the primary (7a-d) and
The reaction of the mesitylphosphatriafulvene 2 with the azides 3a-k yields the ring-enlarged 1H-2-iminophosphetes 6a-k; the structure of 6j was irrevocably established by an X-ray crystal structure analysis. In some cases, 1,3-diphosphetanes (8b-e) have been characterized as by-products.
Electrophilic reagents attack the phosphatriafulvenes 1a and 1b exclusively at the phosphorus atom. Hence 1b is methylated by methyl iodide to furnish the cyclopropenylium iodide 3 which, in turn, is converted to the triazine 6 by reaction with sodium azide. Ketenes 8 react with 1a through subsequent P → O silyl shifts to give the vinylphosphatriafulvenes 10. Isocyanates 13a and 13b behave analogously (→ 15). In the reactions of 1a with isothiocyanates 13c and 13d, in contrast, a P → N silyl shift is observed which leads to the formation of 16. Acetylenedicarboxylates 17 undergo insertion into the P/Si bond of the silylated phosphatriafulvene 1a (→ 19). In the case of the reaction of the mesitylsubstituted phosphatriafulvene 1b with 17, kinetically controlled formation of the dihydrooxophosphinines 20 takes place; at room temperature, the latter products undergo slow rearrangement to give the thermodynamically more stable isomers 21.
Phosphatriafulvenes - phosphaalkenes with inverse electron density
作者:Eberhard P.O. Fuchs、Heinrich Heydt、Manfred Regitz、Wolfgang W. Schoeller、Thilo Busch
DOI:10.1016/s0040-4039(01)93461-6
日期:——
The phosphatriafulvenes 3a,b, accessible from the cyclopropenone 1 and the lithium phosphides 2, possess inverse electron density as indicated by structure B; this can also be deduced from calculations. In accord with the electronicstructure, methyllithium attacks at a carbon atom of the three-membered ring (to ), carboxylic acid chlorides effect -acylation (to 6), and dimethyl acetylenedicarboxylate