Steven s rearrangement

The treatment of betaines with concentrated sulfuric acid leads to the corresponding derivatives of 5-nitroindazole (products of alkylhalogenides elimination). Heating of betaines results in other nitroindazoles a product of Steven s rearrangement or a mixture of N,0- and N,N-atkyl shift products, as shown in Scheme 2.40 [328],... 

A carbanionic mechanism similar to that proposed by Wittig and Krauss (33) involving a Steven s rearrangement can reasonably follow (Equation 5), i.e., an intramolecular attack on ylide (III) methyl forming dimethylethylamine. Protonation of dimethylethylamine followed by Hoffmann elimination (Equation 5a) would yield ethylene. 

Red-Al behaves as a base in certain applications, /fa readily reducible functional group is not present in the molecule. Kametani used Red-Al to induce a Steven s rearrangement (sec. 8.8.C.ii) of berbine methiodide (88) to spirobenzylisoquinoline (89) (9.4%) plus 90 (22.5%). 3 The yield of rearranged products was poor, which is typical for this application of Red-Al. 

Pyridinoparacyclophane-l,9-diene, in which the two aromatic rings are perpendicular, has been prepared by the Steven s rearrangement route. 

Stabilized ester ylides can undergo several possible reactions on heating. Heating (6a) to 155 led to a Steven s rearrangement product (25). Migration preference is shown when one group on sulphur is especially stabilized, in that (6c) afforded (25c) and (6d) afforded (25d). In the latter... 

In addition to an elimination reaction and a Steven s rearrangement, the other major alternative for ylide rearrangement, especially with the presence of a point of unsaturation in the molecule, is a cyclic sigmatropic rearrangement, called either a 1,5- or a 2,3-rearrangement, which was... 

The rearrangement of ammonium ylides (Stevens-Sommelet rearrangement) or sulfonium ylides the X-Y fragment is an anion a to a positively charged nitrogen (R3 N- CR2) or sulfur (R2,+S- CR2)... 

The reactions of sulphimides studied recently concern the kinetics of the reaction between PhSH and JV-toluene-p-sulphonyl-sulphimides - to give PhSSPh, or RSPh (other differences exist between the results from these two studies) the formation of vinyl sulphides by treatment of JV-toluene-p-sulphonyl aryl ethyl sulphimides with Bu OK [TsN=S(Et)Ar -> CHg= CHSAr] the halide-ion-induced Stevens-type rearrangement to the sulphen-amide [TsN=SRAr -> RN(Ts)SAr] and the S-substitution or Pummerer rearrangement products from iV-toluene-/j-sulphonyl-sulphimides by cleavage with NaOH or NaOMe in MeOH. °... 

For a review, see Stevens, T.S. Watts, W.E. Selected Molecular Rearrangements Van Nostrand-Reinhold Princeton, 1973, p. 192. 

For books, see Mayo, P. de Rearrangements in Ground and Excited States, 3 vols. Academic Press NY, 1980 Stevens, T.S. Watts, W.E. Selected Molecular Rearrangements Van Nostrand-Reinhold Princeton, 1973. For a review of many of these rearrangements, see Collins, C.J. Eastham, J.F. in Patai The Chemistry of the Carbonyl Group, vol. 1 Wiley NY, 1966, p. 761. See also the series Mechanisms of Molecular Migrations. 

Simple 1,2-shifts of alkyl, from carbon to carbon, that are carbanionic in character are essentially unknown. Examples are known, however, in which alkyl is involved in a 1,2-shift from other atoms such as N and S to a carbanion atom—the Stevens rearrangement ... 

SHORTER, J. Correlation Analysis in Organic Chemistry (OUP, 1973). STEVENS, T. s. and WATTS, N. E. Selected Molecular Rearrangements (Van Nostrand Reinhold, 1973). 

With phenylsilylated salts, the same type of /V,/V-d i m e t h y I b e n z y I a m i n e s are formed accompanied by /V,/V-d i meth yi -2-1ri meth y I s i I yi meth y I benzyi am i ne. A mechanism involving silylated and non-silylated intermediate ylid has been proposed. Using LAH in place of sodium amide induces cleavage of the silyl group, especially in the triphenylsilyl case. With w-butyllithium, the same two products are obtained in equal amounts accompanied with a Stevens rearrangement product as a minor compound. 

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