Diphenyl diselenide

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Diphenyl diselenide
Chemical structure of diphenyl diselenide
Space-filling model
Identifiers
CAS number 1666-13-3 YesY
PubChem 15460
ChemSpider 14710 YesY
RTECS number JM9152500
Jmol-3D images Image 1
Properties
Molecular formula C12H10Se2
Molar mass 312.13 g mol−1
Appearance Orange powder
Density 1.84 g/cm3
Melting point 59 to 61 °C (138 to 142 °F; 332 to 334 K)
Solubility in water Insoluble
Solubility in other solvents Dichloromethane
Structure
Coordination
geometry
90° at Se[citation needed]
C2 symmetry[citation needed]
Dipole moment 0 D
Hazards
R-phrases R23/25 R33 R50/53
S-phrases S20/21 S28 S45 S60 S61
Main hazards Toxic
Related compounds
Related compounds Ph2S2,
C6H5SeH
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Diphenyl diselenide is the chemical compound with the formula (C6H5)2Se2, abbreviated Ph2Se2 This orange-coloured solid is the oxidized derivative of benzeneselenol. It is used as a source of the PhSe unit in organic synthesis.

Ph2Se2 is prepared by the oxidation of benzeneselenoate, the conjugate base of benzeneselenol which is generated via the Grignard reagent:[1]

PhMgBr + Se → PhSeMgBr
2 PhSeMgBr + Br2 → Ph2Se2 + 2 MgBr2

The molecule has idealized C2-symmetry, like hydrogen peroxide and related molecules. The Se-Se bond length of 2.29 Å the C-Se-Se-C dihedral angle is 82° and the C-Se-Se angles are near 110°.[2]

Reactions[edit]

One reactions characteristic of Ph2Se2 is its reduction:

Ph2Se2 + 2 Na → 2 PhSeNa

PhSeNa is a useful nucleophile used to introduce the phenylselenyl group by nucleophilic substitution of alkyl halides, alkyl sulfonates (mesylates or tosylates) and epoxides. The example below was taken from a synthesis of morphine.[3]

NaSePh-Epoxide1.svg

Another characteristic reaction is chlorination:

Ph2Se2 + Cl2 → 2 PhSeCl

PhSeCl is a powerful electrophile, used to introduce PhSe groups by reaction with a variety of nucleophiles, including enolates, enol silyl ethers, Grignard reagents, organolithium reagents, alkenes and amines. In the sequence below (early steps in the synthesis of Strychnofoline), a PhSe group is introduced by reaction of a lactam enolate with PhSeCl.[4] This sequence is a powerful method for the conversion of carbonyl compounds to their α,β-unsaturated analogs.[5]

ClSePh-enone1.svg

Diphenyl diselenide itself is also a source of a weakly electrophilic PhSe group in reactions with relatively powerful nucleophiles like Grignard reagents, lithium reagents and ester enolates (but not ketone enolates or weaker nucleophiles). PhSeCl is both more reactive, and more efficient, since with Ph2Se2 half of the selenium is wasted.

Ph2Se2 + Nu → PhSeNu + PhSe

N-Phenylselenophtalimide (N-PSP) can be used if PhSeCl is too strong and diphenyl diselenide is too weak or wasteful.[6]

Safety[edit]

Organoselenium compounds are toxic.

References[edit]

  1. ^ Reich, H. J.; Cohen, M. L.; Clark, P. S. (1979), "Reagents for Synthesis of Organoselenium Compounds: Diphenyl Diselenide and Benzeneselenenyl Chloride", Org. Synth. 59: 141 ; Coll. Vol. 6: 533 
  2. ^ Marsh, R. E. (1952). "The Crystal Structure of Diphenyl Diselenide". Acta Crystallographica 5 (4): 458–462. doi:10.1107/S0365110X52001349.  edit
  3. ^ Taber, D. F.; Neubert, T. D.; Rheingold, A. L. (2002). "Synthesis of (−)-Morphine". Journal of the American Chemical Society 124 (42): 12416–12417. doi:10.1021/ja027882h. PMID 12381175.  edit
  4. ^ Lerchner, A.; Carreira, E. M. (2002). "First Total Synthesis of (±)-Strychnofoline via a Highly Selective Ring-Expansion Reaction". Journal of the American Chemical Society 124 (50): 14826–14827. doi:10.1021/ja027906k. 
  5. ^ Reich, H. J.; Wollowitz, S. (1993). "Preparation of α,β-Unsaturated Carbonyl Compounds and Nitriles by Selenoxide Elimination". Organic Reactions 44: 1–296. doi:10.1002/0471264180.or044.01. 
  6. ^ Barrero, A. F.; Alvarez-Manzaneda, E. J.; Chahboun, R.; Corttés, M.; Armstrong, V. (1999). "Synthesis and Antitumor Activity of Puupehedione and Related Compounds". Tetrahedron 55 (52): 15181–15208. doi:10.1016/S0040-4020(99)00992-8.