Lawesson's reagent



















































































Lawesson's reagent

Lawesson's reagent

3D model of the Lawesson's reagent molecule
Names

IUPAC name
2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide


Preferred IUPAC name
2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-dithione

Other names
Lawesson reagent; LR

Identifiers

CAS Number



  • 19172-47-5 ☑Y


3D model (JSmol)


  • Interactive image


ChemSpider


  • 79346 ☑Y


ECHA InfoCard

100.038.944


PubChem CID


  • 87949





Properties

Chemical formula


C14H14O2P2S4

Molar mass
404.45 g·mol−1
Appearance
Slightly yellow powder

Melting point
228–231 °C (442–448 °F; 501–504 K)

Solubility in water

Insoluble
Hazards


EU classification (DSD) (outdated)

Irritant
Harmful (XN)

R-phrases (outdated)

R15/29-R20/21/22

S-phrases (outdated)

S7/8-S22-S45
Related compounds

Related thiation agents


Hydrogen sulfide,
Phosphorus pentasulfide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).


☑Y verify (what is ☑Y☒N ?)

Infobox references



Lawesson's reagent, or LR, is a chemical compound used in organic synthesis as a thiation agent. Lawesson's reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a systematic study of the reactions of arenes with P4S10.[1]




Contents






  • 1 Preparation


  • 2 Mechanism of action


  • 3 Applications


  • 4 See also


  • 5 References


  • 6 External links





Preparation


Lawesson's reagent is commercially available. It can also be conveniently prepared in the laboratory by heating a mixture of anisole with phosphorus pentasulfide until the mixture is clear and no more hydrogen sulfide is formed,[2] then recrystallized from toluene or xylene.


As Lawesson's reagent has a strong and unpleasant smell, it is best to prepare the compound within a fume-hood and to treat all glassware used with a decontamination solution before taking the glassware outside the fume-hood. One common and effective method of destroying the foul smelling residues is to use an excess of sodium hypochlorite (chlorine bleach).



Mechanism of action


Lawesson's reagent has a four membered ring of alternating sulfur and phosphorus atoms. With heating, the central phosphorus/sulfur four-membered ring can open to form two reactive dithiophosphine ylides (R-PS2). Much of the chemistry of Lawessons's reagent is in fact the chemistry of these reactive intermediates.


Dithia.png

In general, the more electron rich a carbonyl is, the faster the carbonyl group will be converted into the corresponding thiocarbonyl by Lawesson's reagent.



Applications


The chemistry of Lawesson's reagent and related substances has been reviewed by several groups.[3][4][5][6] The main use of Lawesson's reagent is the thionation of carbonyl compounds. For instance, Lawesson's reagent will convert a carbonyl into a thiocarbonyl.[7] Additionally, Lawesson's reagent has been used to thionate enones, esters,[8]lactones,[9]amides, lactams,[10] and quinones.


Thionation of a ketone to give a thioketone using Lawesson's reagent

In one study, reaction of maltol with LR results in a selective oxygen replacement in two positions.[11]


Maltol reaction with LR

A combination of silver perchlorate and Lawesson's reagent is able to act as an oxophilic Lewis acid with the ability to catalyze the Diels-Alder reaction of dienes with α,β-unsaturated aldehydes.


Alcohols may be converted to thiols by treatment with Lawesson's reagent.[12]


Lawesson's reagent reacts with sulfoxides to form a thio product, which are then desulfurized to form thioethers.[citation needed] Therefore, it can be used as a reducing agent for sulfoxide.



See also


  • Woollins' reagent


References





  1. ^ Lecher, H. Z.; Greenwood, R. A.; Whitehouse, K. C.; Chao, T. H. (1956). "The Phosphonation of Aromatic Compounds with Phosphorus Pentasulfide". J. Am. Chem. Soc. 78 (19): 5018. doi:10.1021/ja01600a058..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}


  2. ^ Thomsen, I.; Clausen, K.; Scheibye, S.; Lawesson, S.-O. (1990). "Thiation with 2,4-Bis(4-methoxyphenyl)-1,3,2,4-Dithiadiphosphetane 2,4-disulfide: N-Methylthiopyrrolidone". Organic Syntheses.CS1 maint: Multiple names: authors list (link) ; Collective Volume, 7, p. 372


  3. ^ Cherkasov, R. A.; Kutyrev, G. A.; Pudovik, A. N. (1985). "Tetrahedron report number 186 Organothiophosphorus reagents in organic synthesis". Tetrahedron (Review). 41 (41): 2567. doi:10.1016/S0040-4020(01)96363-X.


  4. ^ Foreman, M.S.; Woollins, J.D. (2000). "Organo-P-S and P-Se heterocycles". J. Chem. Soc., Dalton Trans. (10): 1533–1543. doi:10.1039/b000620n.


  5. ^ Martin Jesberger; Thomas P. Davis; Leonie Barner (2003). "Applications of Lawesson's Reagent in Organic and Organometallic Syntheses". Synthesis (Review). 2003 (13): 1929–1958. doi:10.1055/s-2003-41447.


  6. ^ Cava, M. P.; Levinson, M. I. (1985). "Thionation reactions of Lawesson's reagents". Tetrahedron. 41 (22): 5061–5087. doi:10.1016/S0040-4020(01)96753-5.


  7. ^ Pedersen, B. S.; Scheibye, S.; Nilsson, N. H.; Lawesson, S.-O. (1978). Bull. Soc. Chim. Belg. (87): 223. Missing or empty |title= (help)CS1 maint: Multiple names: authors list (link)


  8. ^ Jones, B. A.; Bradshaw, J. S. (1984). "Synthesis and reduction of thiocarboxylic O-esters". Chem. Rev. (Review). 84 (84): 17. doi:10.1021/cr00059a002.


  9. ^ Scheibye, S.; Kristensen, J.; Lawesson, S.-O. (1979). "Studies on organophosphorus compounds—XXVII Synthesis of thiono-, thiolo- and dithiolactones". Tetrahedron. 35 (35): 1339–1343. doi:10.1016/0040-4020(79)85027-9.CS1 maint: Multiple names: authors list (link)


  10. ^ Shabana, R.; Scheibye, S.; Clausen, K.; Olesen, S. O.; Lawesson, S.-O. (1980). Nouveau Journal de Chimie. 1980 (4): 47. Missing or empty |title= (help)CS1 maint: Multiple names: authors list (link)


  11. ^ Brayton, D.; Jacobsen, F. E.; Cohen, S. M.; Farmer, P. J. (2006). "A novel heterocyclic atom exchange reaction with Lawesson's reagent: a one-pot synthesis of dithiomaltol". Chemical Communications. 2006 (2): 206–208. doi:10.1039/b511966a. PMID 16372107.


  12. ^ Nishio, Takehiko (1989). "A novel transformation of alcohols to thiols". Journal of the Chemical Society, Chemical Communications. 1989 (4): 205–206. doi:10.1039/C39890000205.




External links



  • "Lawesson's Reagent". Organic Chemistry Portal. Retrieved 2007-10-16.



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