Lawesson reagent for selenium fans: Phosphorus selenium heterocycles and, in particular, [PhPSe(2)](2) (known as Woollins' reagent) are proving valuable in the synthesis of new heterocycles and for the insertion of selenium into organic substrates. Incorporation of phosphorus and selenium atoms into the products leads to a surprising variety of structures.Phosphorus-selenium ring chemistry has developed to include the synthesis of some exciting new motifs and provided organic chemists with a new reagent, [PhPSe(2)](2), which has become known as Woollins' reagent.

The reaction of hydrazide with carbonyl chloride in the presence of sodium carbonates leads to the corresponding 1,2‐diacylhydrazines [1a–t, R1C(O)NHNHC(O)R2, R1 = aryl, R2 = aryl or alkyl] in moderate to excellent yield (57–90 %). The latter reacts with 2,4‐diphenyl‐1,3‐diselenadiphosphetane‐2,4‐diselenide (Woollins' reagent, WR) in refluxing toluene to give a series of new 2,5‐disubstituted 1,3,4‐selenadiazoles (2a–t, 51–99 % yield). All compounds were characterized spectroscopically and six compounds were characterized crystallographically. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

[Structure: see text] The reaction of aryl nitriles with Woollins' reagent followed by water affords a variety of primary arylselenoamides in 60-100% yield. The first crystal structures of two primary selenoamides are reported.

Organoselenium compounds are studied because of their interesting reactivities and potential biological or pharmaceutical significance. Organic diselenides, as useful synthetic reagents and intermediates, have played an important role in organoselenium chemistry, as they are stable, easily handled, and reactive enough to generate electrophilic, nucleophilic, and radiophilic species.[1] There are only a few examples of macrocycles containing diselenide linkages, [2] and many of the known routes to diselenides in general suffer from the use of highly toxic H 2 Se, harsh reaction conditions, low yields, or complicated manipulations.We are developing the chemistry of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [PhP(Se)(m-Se)] 2 (known as Woollins reagent, WR).[3] Herein, we report the synthesis of five novel P À Se diselenides with eight-, nine-and ten-membered rings; this is the first reported synthesis of such large-ring diselenides bearing the P-Se-Se-P linkage.Cleavage of the four-membered P 2 Se 2 ring in WR by alkyl diols affords the corresponding bis(diselenophosphonic) acids quantitatively as yellow oils. These acids were converted into the corresponding amine salts by treatment with butylamine and were oxidized using I 2 /KI to give eight-, nine-and tenmembered-ring diselenides 1-3 (70-90 % yields, Scheme 1).Compounds 1-3 are soluble in common polar organic solvents and were crystallized from dichloromethane solutions with slow diffusion of hexane to give transparent, colorless, cubic crystals. The compounds are stable to air and moisture for several months. The 31 P NMR spectra of 1-3 exhibit sharp singlets at d % 67 ppm, which are accompanied by two sets of satellites for the endocyclic and exocyclic selenium atoms ( 1 J(P,Se endo ) and 1 J(P,Se exo ): 444 and 822 Hz for 1, 465 and 812 Hz for 2, and 460 and 808 Hz for 3), thus indicating the presence of single and double PÀSe bonds in each compound. Detailed NMR spectroscopic analysis reveals the relatively small coupling constant between phosphorus atoms ( 3 J(P,P) = 3.0-4.7 Hz), supporting the presence of the P-Se-Se-P group (cf.3 J(P,P) = 4 Hz for the analogous P-S-S-P system).[4] The 77 Se NMR spectra for 1-3 contain signals arising from exocyclic (d = À75, À61, and À80 ppm; 1 J(P,Se exo ) = 822, 810, and 806 Hz, respectively) and endocyclic selenium atoms (d = 491, 441, and 441 ppm). The X-ray structures of 1-3 (Figure 1) confirm the presence of the eight-, nine-, and ten-membered rings. Both R,R and S,S enantiomers are present in all the structures, and no R,S/S,R diastereomers are observed. The macrocyclic framework is highly puckered with the two phenyl rings on opposite sides of the heterocycle. The Se À Se bond (2.3393(12), 2.3518(7), and 2.3475(6) in 1-3, respectively) is slightly shorter than that in acyclic structures containing the P-Se-Se-P linkage (2.384(1) ).[5] The geometry around P(1) and P(2) is distorted tetrahedral (Se(1)-P(1)-Se(2) and Se(3)-P(2)-Se(4): 103.94(9) and 105.25(9), 105.49(6) and 105.76(6), 103.94(9) and 106....

Four-membered ring [PhP(Se)(μ-Se)]2 (Woollins' reagent, WR) reacts with disodium alkenyl-diols followed by in situ ring-closure reaction with appropriate dibromoalkanes affording a series of unusual nine- to fifteen-membered organoselenophosphorus macrocycles bearing the O-P-Se-Cn-Se-P-O or O-P-Se-Cn-O-P-Se linkage.

No abstract

The first of its kind? A simple, twelve‐membered C‐Se heterocycle (see structure; blue C, yellow Se, black H) was obtained by treatment of secondary amines with Woollins' reagent. The ring formation proceeds through diselenoate intermediates and requires a polar solvent like dichloromethane.

Reaction of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [PhP(Se)(mu-Se)](2) (Woollins' reagent, WR) with one equivalent of 1,4-diarylbutane-1,4-diones 1a-g in refluxing toluene affords the corresponding 2,5-diarylselenophenes 2a-g in excellent yields (up to 99%). Alternatively, the 2,5-diarylselenophenes (2a and 2b) can be obtained in 70-80% yields from the reaction of arylacetylene with an equivalent of O-methyl Se-hydrogen phenylphosphonodiselenoate; the latter was derived from WR and methanol. The first X-ray structure of 2,5-diarylselenophenes is presented along with characterisation of their redox properties.