TRANSANNULAR AND HYDROGEN-REARRANGEMENT REACTIONS IN CARBENOID DECOMPOSITION OF DIAZOCYCLOALKANES

1961 ◽  
Vol 83 (14) ◽  
pp. 3159-3160 ◽  
Author(s):  
Lester Friedman ◽  
Harold Shechter
Keyword(s):  
Rearrangement Reactions ◽  
Hydrogen Rearrangement

Is the collision induced loss of ethene from the (M – H+)− ion of butyrophenone a γ-hydrogen rearrangement?

1986 ◽  
Vol 64 (4) ◽  
pp. 764-768 ◽  
Author(s):  
Michael B. Stringer ◽  
Dennis J. Underwood ◽  
John H. Bowie ◽  
John L. Holmes ◽  
Alexander A. Mommers ◽  
...  
Keyword(s):  
Collisional Activation ◽  
Hydrogen Atoms ◽  
Rearrangement Reactions ◽  
Hydrogen Rearrangement ◽  
Hydrogen Scrambling

The (M – H+)− ion of butyrophenone undergoes the following reactions on collisional activation: losses of CH3•, CH4, (C,H5•), C2H4, C3H7•, (CO + CH4), together with formation of C6H5− and C4H5O−. Labelling studies (13C and 2H) show that the losses of CH3•, C3H7• and the formation of C6H5− and C4H5O− are specific and occur without hydrogen scrambling. All other reactions involve prior or accompanying hydrogen rearrangement. In particular, the loss of C2H4 is very complex: it involves loss of ethyl carbon atoms, but all hydrogen atoms are involved via specific rearrangement reactions. The phenyl–alkyl H rearrangements which are noted for this process occur after collisional activation of the (M – H+)− ion.

Interaction of heterocycles and nucleophiles. II. Sigma complexes formed from methoxide ion and Methoxy-3,5-dinitropyridines in dimethyl sulphoxide

1970 ◽  
Vol 23 (5) ◽  
pp. 957 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
AG Moritz ◽  
DB Paul
Keyword(s):  
Dimethyl Sulphoxide ◽  
No Conversion ◽  
Solvation Effects ◽  
Sigma Complexes ◽  
Sigma Complex ◽  
Methoxide Ion ◽  
Rearrangement Reactions

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.

scholarly journals Recent development and applications of semipinacol rearrangement reactions

2021 ◽  
Author(s):  
Xiao-Ming Zhang ◽  
Bao-Sheng Li ◽  
Shao-Hua Wang ◽  
Kun Zhang ◽  
Fu-Min Zhang ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Quaternary Carbon ◽  
Carbon Formation ◽  
Semipinacol Rearrangement ◽  
Rearrangement Reactions

The recent development of semipinacol rearrangement is reviewed, highlighting its application in β-functionalized ketone synthesis, quaternary carbon formation and total synthesis.

Catalyst-Free [2,3]-Sigmatropic Rearrangement Reactions of Photochemically Generated Ammonium Ylides

Synthesis ◽  
2019 ◽  
Vol 51 (23) ◽  
pp. 4348-4358 ◽  
Author(s):  
Fang Li ◽  
Feifei He ◽  
Rene M. Koenigs
Keyword(s):  
Visible Light ◽  
Sigmatropic Rearrangement ◽  
Tertiary Amines ◽  
Amino Esters ◽  
Catalyst Free ◽  
Rearrangement Reaction ◽  
Rearrangement Reactions ◽  
Free Ammonium

The rearrangement reaction of ammonium ylides furnishes valuable α,α-disubstituted amino esters. In this work, we describe the visible-light photolysis reaction of aryldiazoacetates in the presence of tertiary amines that react via a free ammonium ylide in a sigmatropic rearrangement reaction to provide amino esters in moderate to very good yields (33 examples, up to 97% yield).

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