Davy s reagent

Bis-(methylthio)-l,3,2X, 4X -dithiadiphosphetane-2,4-dithione (Davy s reagent) [82737-61-9] M 284.4, m 160°. Recrystd from C6H6 in yellow plates or from hot trichlorobenzene. The low m observed in the literature (112° with gradual softening at 68-102°) has been attributed to the presence of elemental sulfur in the crystals. [Tetrahedron 40 2663 1984 J Org Chem 22 789 1957.]... 

Stereoselective addition of cuprates to ji-alkoxy enoates of type 49 [17] isee Sdiemes 6.8 and 6.9) bas been used in die crrnstruction of polypropionate-type structures. Tlius, a sequence of diastereoselective cuprate addition, etiolate for-ruabon, and diastereoselective oxygenation widi Davis s reagent bas been applied iteratively to provide a Cio segment of Rifaruycin S i60) [ 17c, d]. 

The p-thiolactams 50 are obtained by the action of Lawesson s or Davy s reagent on 3-substituted 1-methoxy- or 1-benzyloxy-azetidinones followed by reductive N-deprotection. The simple P-thiolactam can be modified to give the thiolactam analogues of monobactams <96LA141>. 

Alvarez-Toledano has also investigated150 the reaction of vinylketene complexes 221.d and 221.g with Davy s reagent, a dimeric species that generates a phosphorus-sulfur yield in situ. This then attacks the ketene carbonyl in a nucleophilic fashion, generating the intermediate 244, which collapses to yield the product (245). 

A particularly convenient one-step conversion of carboxylic acids into dithioesters [140, 141] makes use of Davy s reagents [142], in which the R2S —P(=S) structural feature permits the two necessary functional group modifications, first OH substitution by SR2, followed by thionation of the C=0 group. 

Conversion of propanoic acid into methyl propanedithioate with Davy s reagent (R2 = Me)... 

Davy s reagents with R2 = Me, Et, i-Pr or PhCH2 have been prepared [142] and used [140, 141]. The first two are commercially available from Fluka and Aldrich. 

In the last decade the methods of converting carbonyl to the corresponding thiocarbonyl compounds have been substantially improved. " Therefore, thioxo- as well as dithio-carboxylic esters are accessible from esters, thiol esters and even carboxylic acids by reacting them with phosphorus pentasul-fide or 1,3,2,4-dithiadiphosphetane 2,4-disulfides such as Lawesson s or Davy s reagent (equation 4 cf. Chapter 4.1, this volume). 

Bis-(methylthio)-l,3,2X, ,4X, -dithiadiphosphetane-2,4-dithione (Davy s reagent methyl)... 

Bis-(p-tolylthio)-l,3,2X ,4X -dithiadiphosphetane-2,4-ditbione (Heimgartner s reagent or Davy s reagent p-tolyl) [114234-09-2] M 436.6, m 175-176. Recrystallise it from toluene... 

---