Observation of a Stable Carbocation in a Consecutive Criegee Rearrangement with Trifluoroperacetic Acid

2000 ◽  
Vol 65 (13) ◽  
pp. 3926-3933 ◽  
Author(s):  
Pavel A. Krasutsky ◽  
Igor V. Kolomitsyn ◽  
Paul Kiprof ◽  
Robert M. Carlson ◽  
Andrey A. Fokin
1975 ◽  
Vol 28 (11) ◽  
pp. 2479 ◽  
Author(s):  
CB Hudson ◽  
AV Robertson ◽  
WRJ Simpson

N-Protected esters of 3,4-dehydro-DL-proline react with trifluoroperacetic acid to give, in high yield, approximately equal amounts of the corresponding stereoisomeric 3,4-epoxy-DL-proline derivatives, direct separation of which proved difficult. However individual members of the two families were obtained by discovery of selective transformations and fractionations. Relative configurations of the two 3,4-epoxy-N-tosylproline methyl esters were established by borohydride reduction to authentic 4-hydroxy-N-tosylprolinols. Epoxide reduction is regioselective. Extensive p.m.r. analyses then permitted stereochemical assignment of other derivatives. These epoxides are remarkably resistant to catalytic hydrogenolysis, and to hydration in acid or alkali. N-Substituted 3,4-epoxyproline methyl esters undergo ready β-elimination in alkali to yield the corresponding 4-hydroxy-2,3- dehydroproline esters and ultimately the N-substituted pyrrole-2- carboxylic acid or ester. Prolonged aqueous acid hydrolysis of 3,4- epoxy-N-tosylprolines, or of their methyl esters, gives mixtures of 3,4-dihydroxy-N-tosyl-DL-prolines in the 2,3-cis-3,4-trans and 2,3- trans-3,4-trans families. Their stereochemistry was allotted from p.m.r. of the diacetate methyl esters. During acid hydrolysis of 3,4- epoxy-N-tosylproline methyl esters, the ester of the trans stereoisomer hydrolyses selectively, and some epimerization of the cis stereoisomer occurs. Ester hydrolysis is much faster than epoxide hydration. Anhydrous acid cleavage of 3,4-epoxy-N-tosyl-DL-proline t-butyl esters to the epoxy acids is unusually slow.


1976 ◽  
Vol 7 (16) ◽  
pp. no-no
Author(s):  
A. A. AKHREM ◽  
P. A. KISELEV ◽  
D. I. METELITSA

Author(s):  
Kenneth C. Caster ◽  
A. Somasekar Rao ◽  
H. Rama Mohan

Author(s):  
L. I. Khmel'nitskii ◽  
T. S. Novikova ◽  
S. S. Novikov

1974 ◽  
Vol 29 (7-8) ◽  
pp. 549-551 ◽  
Author(s):  
Monika Gladys ◽  
Wolfgang-R. Knappe

The direct synthesis of (iso)alloxazine N-oxides using trifluoroperacetic acid in situ is reinvestigated, showing sensitivity towards steric (peri) hindrance. The photoreduction of these N-oxides in the presence of 1,4-cyclohexadiene yields the parent (iso)alloxazine. The reduction of the N-oxides by initially formed dihydro (iso)alloxazine is ruled out for the photoreduction.


ChemInform ◽  
2005 ◽  
Vol 36 (38) ◽  
Author(s):  
Pavel A. Krasutsky ◽  
Igor V. Kolomitsyn

1999 ◽  
Vol 35 (1) ◽  
pp. 75-79
Author(s):  
N. V. Kovganko ◽  
D. V. Drozdov ◽  
S. K. Ananich

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