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Addition Reactions of Phosphorus Nucleophiles to Benzothiete
Eckes, Heinz-Ludwig,Niedermann, Hans-Peter,Meier, Herbert
, p. 377 - 381 (2007/10/02)
Trialkyl phosphites 4 add to the o-quinoid form 2 of benzothiete (1) to yield the phosphonates 6.An intermolecular migration of an alkyl group from oxygen to sulfur is the most important feature of this transformation.The rearrangement - related to the Arbuzov reaction - can be avoided in a two-step process by the subsequent action of PCl3 and alcohol; thus the phosphonates 10 are generated.Analoguos to 2 -> 6, dimethyl phenylpghosphinate (11) furnishes 13.In contrast, the cyclic esters 14a-d form 2:1 adducts, namely the 12- to 15-membered heterocyclic compounds 17a-d.An intramolecular rearrangement in a 1:1 adduct is only observed for the 1,3,2-dioxaphosphepine 14e, a benzylic system which allows an SN1 process generating the 1,6,2-oxathiaphosphecine 18e.A similar rearrangement at a tertiary carbon center is prevented by the competitive addition of water (1 + 14f -> 20).
