Phosphonyl, Phosphonothioyl, Phosphonodithioyl, and Phosphonotrithioyl Radicals:  Generation and Study of Their Addition onto Alkenes

Abstract

The treatment of benzyl dialkyl phosphites and dithiophosphites with benzeneselanyl chloride generates an Arbuzov-type transformation leading to the dialkyl selenophosphates 19a and 19b and to selenophosphorodithioates 21a and 21b. Interaction of these substrates with Lawesson's reagent yields the corresponding selenophosphorothioates 20a and 20b and the selenophosphorotrithioates 22a and 22b. When treated with a radical initiator in the presence of a hydrogen donor and an alkene, all eight phosphorus(V) precursors undergo homolytic cleavage of the P−Se bond to generate the phosphonyl, phosphonothioyl, phosphonodithioyl, or phosphonotrithioyl radicals. Most of these are shown to add onto electron-rich and electron-poor alkenes to deliver the expected adducts in fair to excellent yields. Cyclic precursor 19b displays peculiar behavior and, under the reaction conditions, produces only the corresponding cyclic phosphite. Application of this radical chain process is carried out on furanosyl 3-exo-methylene derivative 37 to diastereoselectively furnish five new 3-phosphonomethyl-, 3-phosphonothiomethyl-, and 3-phosphonodithiomethyl-3-deoxofuranoses 38a−c and 38f,g. The possibility of conducting tandem processes is also discussed through experiments involving (1R)-(+)-α-pinene (39) and diallylamine 41.

Recent advances in sulfur- and phosphorous-centered radical reactions for the formation of S–C and P–C bonds

“…232 The Piettre group has been leading the effort on using selenophosphonates as precursors to generate diethyl phosphonyl, diethyl phosphonothioyl, and S,S-dialkyl phosphonyl radicals for the reactions with alkenes. 167 The reactions were promoted with n-Bu 3 SnH or tris(trimethylsilyl)silane (TTMSSH) in the presence of AIBN to form products 312-314…”

(Me3Si)3SiH: Twenty Years After Its Discovery as a Radical‐Based Reducing Agent

“…Although the reaction with 1-methylene cyclohexane is efficient with all four derivatives, a different selectivity is observed with electron-rich or electron-poor alkenes. [35] An example of efficient two-step annelation of functionalized orthoesters with trimethylsilyloxyfuran derivatives to produce bicycloA C H T U N G T R E N N U N G [3.n.0]lactones [36] is given in Scheme 12. The radical cyclization and the subsequent hydrogen abstraction to afford 9 occurs efficiently and with complete diastereocontrol, resulting in two contiguous stereocenters generated with > 95 % stereoselectivity.…”

Analogues of nucleotides and oligonucleotides featuring difluorophosphonate, difluorophosphonothioate and difluorophosphinate functional groups

“…The electronic influence of the ether group on this reaction might thus be indicative of the electrophilic nature of phosphonyl and phosphonothioyl radicals, and has a strong effect on the course of the reaction by overcoming the electronic and steric action of the fluorine atoms [32]. It is noteworthy that the unfluorinated analogue of 51 undergoes efficient addition of both phosphonyl and phosphonothioyl radicals to deliver the expected adducts in good to excellent yields [33].…”