[32133-82-7] · C30H20F12O2S · Diphenylbis(1,1,1,3,3,3-hexafluoro-2-phenyl-2-propoxy)sulfurane · (MW 672.57)
Physical Data: mp 107-109 °C.
Solubility: sol ether, benzene, acetone, alcohols.
Form Supplied in: white crystals.
Analysis of Reagent Purity: NMR, IR.
Preparative Method: by the reaction of the potassium salt of 1,1,1,3,3,3-hexafluoro-2-phenylisopropanol with diphenyl sulfide in the presence of chlorine in ether at -78 °C.1a
Handling, Storage, and Precautions: avoid moisture; readily hydrolyzed; stable at rt; decomposes slowly at rt in solution.
The title reagent (1) is useful for the dehydration of alcohols. In general, tertiary alcohols are dehydrated instantaneously at rt. Some secondary alcohols are dehydrated. In cyclohexane rings, a trans-diaxial orientation of the leaving groups significantly increases the rate of elimination (eq 1). Primary alcohols do not yield products of dehydration unless the b-proton is sufficiently acidic. In most cases, the ether [(CF3)2PhCOR] is obtained.2
Vicinal diols, capable of attaining an antiperiplanar relationship, can be converted to epoxides (eq 2). The reaction requires 1-2 equiv of (1) in chloroform, ether, or carbon tetrachloride and takes place at rt. The reaction is postulated to take place via ligand exchange with the sulfone followed by decomposition to the epoxide, diphenyl sulfoxide, and 1,1,1,3,3,3-hexafluoro-2-phenylisopropanol.
Other cyclic ethers have been prepared, but yields are highly dependent on product ring size. The following transformations are representative: 2,2-dimethyl-1,3-propanediol to 3,3-dimethyloxetane (86%), 1,4-butanediol to tetrahydrofuran (72%), 1,5-pentanediol to tetrahydropyran (39%), and diethylene glycol to dioxane (40%). Longer chain diols yield ethers [(CF3)2PhCO(CH2)
Eschenmoser used this method to convert (5R,6R)-5,6-dihydro-b,b-carotene-5,6-diol to its epoxide (eq 3). This reagent is more effective than other reagents due to the unique solubility profile of the dihydrocarotenediol.4
Secondary amides can be converted to esters with (1). The rate is sensitive to steric constraints at the nitrogen and the acyl carbon. In most cases the amine portion is trapped as the sulfilimine and/or the imidate, which are easily converted back to the amine (eq 4). The dual nature of this reaction affords a mild conversion of amides to esters as well as a simple method for deprotection of N-acylated amines.5
In a related reaction, (1) reacts with primary amines (as well as amides and sulfonamides) to give sulfilimines (eq 5). Secondary amines are converted to imines on reaction with (1) whereas benzylamine is converted to benzonitrile (89%) with 2 equiv of (1).6
Brian A. Roden
Abbott Laboratories, North Chicago, IL, USA