Rearrangement Stephens

The first preparation of a stibonium ylide was probably achieved in 1953. When dibenzyldimethylstibonium bromide was treated with phenyllithium, the product obtained was dimethyl(l,2-diphenylethyl)stibine which could arise from a Stephens rearrangement of the expected ylide (see equation 45) addition of the phenyllithium first of all afforded a yellow colour which rapidly disappeared. 

Acids or salts are utilized directly in Stephen s method 166 (iii) reaction with 3-chlorobenz[d]isothiazole-1,1-dioxide (6) (pseudosaccharin chloride3,166). The initial step is presumably formation of 29, followed by Mumm rearrangement. Frequently one obtains pseudosaccharin anhydride (32)25,162 as a by-product. From the reactions with silver acetate and below 3° only A-acetylsaccharin (33) besides 32 was isolated.167 In this context reexamination of the reported 3-O-benzene-sulfonylbenz[d] isothiazole-1,1-dioxide42 and the supposed 3-O-benzoyl... 

One of the classical reductive aldehyde syntheses is the Sonn-MUller reduction of imidoyl chlorides. The method is closely related to the Stephen reduction described in the previous section. As shown in Scheme 16, substrates (53) may be prepared either by the treatment of anilides with phosphorus pentachloride or sulfinyl chloride, or less usually via the Beckmann rearrangement. They are... 

Anion-Assisted Sigmatropic Rearrangements Stephen R, Wilson... 

In an interesting experiment, it was demonstrated by Stephen and Marcus187 that sulfenes prefer to add to electron-rich olefins in a [2 + 2] manner even when other pathways are available. In a dienaminoketone (88) there are two alternative ways in which a sulfene can react (a) to form a [4 + 2] adduct with the enaminoketone or (b) to give the usual [2 + 2] adduct with the enamine double bond. In fact the sulfene insertion product (89) was formed, presumably by the rearrangement of the [2 + 2] cycloadducts 90 and 91 as shown in equation 68. 

Stephen R. Wilson and Corinne E. Augelll 210 THE CARROLL REARRANGEMENT 5-DODECEN-2-ONE... 

CONTENTS Introduction to the Series An Editor s Foreword, Albert Padwa. Preface, Dennis P. Curran. Steiic Course and Mechanism of 1,3-Dipolar Cycloadditions, Rolf Huisgen. Nonstabilized Azomethine Ylides, Edwin Vedejs. Molecular Rearrangements Occurring from Products of Intramolecular 1,3 Dipolar Cycloadditions Synthetic and Mechanistic Aspects, Arthur G. Schultz. Dipolar Cycloadditions of Nitrones with Vinyl Ethers and Silane Derivatives, Philip DeShong, Stephen N. Lander, Jr., Joseph M. LeginusandC. Michael Dickson. The Cycloaddition Approach to b-Hydroxy Carbonyls An Emerging Alternative to the Aldol Strategy, Dennis P. Curran. Index. 

Stephen, T., and H. Stephen The Beckmann Rearrangement of cyclo Pentanone Oxime. J. Chem. Soc. 1956, 4694. 

Camps Quinoline Synthesis Cannizzaro Reaction Carbylamine Reaction Carroll Rearrangement Castro Reaction Castro-Stephens Coupling CBS... 

R. Stephen Berry answered this question seven years later when he recognized that this exchange was an example of pseudorotation, when atoms that lie in a circle oscillate perpendicular to that circle, mimicking rotation. (Fans doing the wave in a baseball stadium are pseudorotating all the motion is actually just up and down, but it conveys an impression of rotation around the stadium.) The motion involved in PF5 is illustrated in Fig. 6.4. This was the first chemical example of pseudorotation discovered, but the motion is associated with many intramolecular rearrangements and even plays a part in chemical reactions such as the hydrolysis of phosphate esters. 

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