Davy-reagent methyl

Related Reagents. 1,3,2,4-Dithiadiphosphetane, 2,4-Bis-(methylthio)-2,4-disulfide (Davy-reagent methyl) 1,3,2, 4-dithiadiphosphetane, 2,4-Bis(ethylthio)-2,4-disulfide (Davy-reagent ethyl) 1,3,2,4-Dithiadiphosphetane, 2,4-Bis(phenyl-thio)-2,4-disulfide 1,3,2,4-Dithiadiphosphetane, 2,4-Bis-[(4-methox3q)henyl)thio]-2,4-disulfide 1,3,2,4-Dithiadiphosphetane, 2,4-bis(4-methoxyphenyl)-2,4-disulfide (Lawesson Reagent). 

A solution of propanoic acid (5.92 g, 80mmol) in 1,2,4-trichlorobenzene (80 ml) was heated at 80-100°C. Davy s methyl reagent (12.6 g, 44 mmol), prepared according to [142], was added portionwise in 2 min. The mixture was heated at 140°C during 10 min (caution operate under a hood and trap obnoxious vapours by bleach). It was then cooled to room temperature. The liquid which separated was distilled to give yellow methyl propanedithioate (5.93 g, 49 mmol, 61%), b.p. 57°C/12 torr. 

Phenylsu onyl) 3 phenytoxazmdine (Davis reagent) 90 Phosphmimine 247,269 Phosphine tiiphenyt 222 359 PhosphSe methyl 8,359 Phosphorus red 163... 

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

Further examples of acyclic stereocontrol in related amino acid systems make use of chiral and nonracemic oxaziridine reagents to induce high levels of stereocontrol. In 1992, Davis and coworkers synthesized the methyl ester of the Taxol C13 side chain using this method.30 Following enolization, the dianion of 44 was reacted with the Davis reagent 5 to yield the a-hydroxy (5-amino acid 45 in 49% yield. While the yield was marginal in this particular example, the 86 14 ratio of stereoisomers produced is impressive in this acyclic system. 

Bis(methylthio)-l,3,2X, 4A, -dithiadiphosphetane-2,4-dithione (Davy s reagent methyl) [82737-61-9] M 284.4, m 160°. It crystallises from C6Hg in yellow plates or from hot trichlorobenzene. The low melting point reported in the literature (112° with gradual softening at 68-102°) has been attributed to the presence of elemental sulfur in the crystals. It has a foul odour and is a suspected carcinogen. [Yousif et al. Tetrahedron... 

In the absence of any added reagents Shelton and Davis (1967, 1973) found that the sulfenic acid slowly disappeared with formation (3) of its anhydride , t-butyl 2-methyl-2-propanethiolsulfinate. The relative slowness of this reaction... 

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

In the former case, almost complete stereoselective oxidation to the chiral selenoxides has been accomplished quite recently. The Davis oxidant, 3,3-di-chloro-l,7,7-trimethyl-2 -(phenylsulfonyl)spirobicyclol2.2.11heptane-2,3 -oxa-ziridine, was found to be the most efficient reagent for the enantioselective oxidation of a variety of prochiral alkyl aryl selenides [81. Asymmetric oxidation was accomplished by the treatment of the selenides with 1 molar equivalent of the Davis oxidant at 0°C to afford the corresponding chiral alkyl aryl selenoxides in quantitative yields with 91-95% ee (Scheme 1). The oxidation of methyl phenyl selenide was complete within 1 min, whereas that of triiso-propyl(a bulkier alkyl) phenyl selenide required a few hours. Typical results are... 

The present procedure for the preparation of oxazolidinone 3 is a variation of the procedures described by Luche" and Davies. Yields have been substantially enhanced by improving the purification procedures. The preparation of 3 starting from valine methyl or ethyl ester hydrochloride has been described by several authors. > > > These procedures suffer from moderate yields for the Grignard addition step and some of them use hazardous reagents like phosgene. 

S. Davies has used an iron complex as an auxiliary for the asymmetric cyclopro-panation of a,P-unsaturated carbonyls [105]. The iron acyl is most stable in the s-cis conformation, as illustrated in Scheme 6.27, in order to avoid severe interactions between the iron ligands and R. Coordination of the Simmons-Smith reagent to the carbonyl oxygen, anti to the iron, forces the alkene moiety out of conjugation and approximately orthogonal to the carbonyl. Because of the bulky triphenyl phosphine in the rear, this rotation can only be towards the front. Transfer of the methylene via the illustrated transition state accounts for the observed diastereoselectivity. Oxidation with bromine removes the iron acyl and derivatization with a-methyl-benzyl amine allowed evaluation of the stereoselectivity. 

---