Eschenmoser hydrazone

The starting material A aziridinyl imine is also known as Eschenmoser hydrazone. 

The starting material A -aziiidinyl imine is also known as Eschenmoser hydrazone. Example 2, Thermal Bamford-Stevens ... 

The development of a tandem rhodium-catalyzed Bamford-Stevens/thermal aliphatic Claisen rearrangement sequence was elegantly demonstrated by Stoltz. As a general method to prepare non-carbonyl-stabilized diazo compounds in situ, this group chose to investigate the decomposition of //-aziridinyl imines (also known as Eschenmoser hydrazones) 28. ... 

Two last elegant examples involving a C-H insertion process have been reported under Rh(II) catalysis. On one hand, N-fiised indolines (107) have been prepared from Eschenmoser hydrazones (108) via the Rh(ll)-catalysed decomposition of the N-aziridinyl imine moiety. ° This C-H insertion methodology has been successfully applied to the total synthesis of ( )-cryptaustoline (109). 

Fragmentation of a.fJ-Epoxy Hydrazones Eschenmoser-Tanabe ring cleavage... 

A 2-cyclohexenone derivative can be transformed into the corresponding epoxy tosyl-hydrazone by sequential treatment with peracid and tosylhydrazine. The elimination of nitrogen and p-toluenesulfinate and fragmentation after rearrangement to the 3-tosylazo allylic alcohol may occur under mild conditions. Carbonyl compounds with 5,6-triple bonds are formed in high yields (J. Schreiber, 1967 M. Tanabe, 1967). If one applies this reaction to a 9,10-epoxy-1-decalone, a ten-membered 5-cyclodecyn-l-one ring is formed (D. Felix, 1971). This product is an important intermediate in the perfume industry and has been used on a large scale. For this purpose Eschenmoser developed a synthesis in which the readily removed styrene was split off instead of a sulfmic acid. Thus a l-amino-2-phenylaziridine hydrazone was used instead of a tosylhydrazone (D. Felix, 1968). ... 

Eschenmoser and his coworkers then went on to introduce other diazo precursors. Two of them were 2-phenylaminoaziridine and // a/w-2,3-diphenylaminoaziridine . The aminoaziridine hydrazones (48) of a-epoxyketones decompose thermally and afford acetylenes in higher yields than the tosylhydrazones . Furthermore, only inert and volatile by-products are formed and the reaction takes place purely... 

The Eschenmoser fragmentation uses a tosyl hydrazone of an cr,/S-epoxy-ketone (p. 1008). epoxide can be made with alkaline hydrogen peroxide and the tosylhydrazone needs tosylhydrazine to form what is simply an imine. Then the fiin can begin. The stereochem y doesn t matter for once. 

Eschenmoser-Tanabe fragmentation Formation of alkynals or alkynones from epoxy ketone hydrazones. 158... 

Eelix, D., Schreiber, J., Piers, K., Horn, U., Eschenmoser, A. New version of epoxy ketone-> alkynone fragmentation. Thermal decomposition of hydrazones from a,P-epoxycarbonyl compounds and W-aminoaziridines. Helv. Chim. Acta 1968, 51, 1461-1465. 

Hydrazones can be readily prepared by the addition of a hydrazine to an aldehyde or ketone. Treatment of tosyl hydrazones (or other arylsulfonyl hydrazones) with a base has been used for the preparation of alkenes. In the Bamford-Stevens reaction, a mild base, such as NaOMe or KH, is employed and promotes deprotonation of the acidic N—H proton (compare with the Eschenmoser fragmentation. Scheme 2.33). 

Eschenmoser has published an extensive account of the fragmentation of ttjff-epoxy-ketones to alkynones numerous examples illustrate the course of thermolysis of hydrazones derived from ajS-epoxy-ketones and substituted aminoaziridines (Scheme 111). This preparatively useful method is also applicable to the preparation of acetylenic aldehydes. 

The fragmentation reaction of Eschenmoser, which gives acetylenes from toluene-p-sulphonyl hydrazones of aj -epoxy-ketones (Scheme 1), has been adapted to the synthesis of acetylenes from ketones substituted with leaving groups in the a-position [(7) -> (8)]. ... 

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