Photochemistry of aromatic .alpha.,.beta.-epoxy ketones. Substituent effects on oxirane ring-opening and related ylide behavior

1985 ◽  
Vol 50 (16) ◽  
pp. 2818-2825 ◽  
Author(s):  
C. V. Kumar ◽  
D. Ramaiah ◽  
P. K. Das ◽  
M. V. George
Keyword(s):  
Ring Opening ◽  
Substituent Effects ◽  
Oxirane Ring ◽  
Alpha Beta ◽  
Epoxy Ketones

Substituent Effects in Mechanochemical Allowed and Forbidden Cyclobutene Ring-Opening Reactions

2021 ◽  
Author(s):  
Cameron L. Brown ◽  
Brandon H. Bowser ◽  
Jan Meisner ◽  
Tatiana B. Kouznetsova ◽  
Stefan Seritan ◽  
...  
Keyword(s):  
Ring Opening ◽  
Substituent Effects ◽  
Ring Opening Reactions

An analysis of the factors contributing to the regioselectivity observed in the opening of oxiranes

1980 ◽  
Vol 58 (3) ◽  
pp. 302-306 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Oxygen Atom ◽  
Ring Opening ◽  
Oxirane Ring ◽  
Epoxide Ring ◽  
Acid Base ◽  
Epoxide Ring Opening ◽  
Soft Acid ◽  
Hsab Theory

The regioselectivity of epoxide ring opening can be analyzed in terms of hard–soft acid–base (HSAB) theory. The coordination of the hard acid with the oxygen atom of the oxirane ring produces a "pulling effect" which determines the direction of the ring opening. In the absence of a strong "pulling effect" the "pushing effect" of the approaching base is examined and the consequences of relative softness or hardness of the nucleophile on the regioselectivity of the ring opening are discussed.

Are amines basic or nucleophilic catalysts for oxirane ring opening by proton-donating nucleophiles?

2016 ◽  
Vol 57 (1) ◽  
pp. 47-51 ◽  
Author(s):  
S. G. Bakhtin ◽  
E. N. Shved ◽  
Yu. N. Bespal’ko
Keyword(s):  
Ring Opening ◽  
Oxirane Ring ◽  
Nucleophilic Catalysts

Total Synthesis of Monosaccharides. Synthesis of Methyl DL-Pentopyranosides with α- and β-lyxo, β-ribo, α-xylo, and α-arabino Configurations from Furfuryl Alcohol

1975 ◽  
Vol 53 (17) ◽  
pp. 2524-2529 ◽  
Author(s):  
Osman Achmatowicz Jr. ◽  
Pawel Bukowski
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Furfuryl Alcohol ◽  
Oxirane Ring

Hydroxylation and epoxidation, followed by the oxirane ring opening, of methyl 2,3-dideoxy-α and β-DL-pent-2-enopyranosides, readily available by the transformation of furfuryl alcohol, afforded the title compounds. Steric course of hydroxylation and epoxidation reactions were examined. The p.m.r. data of methyl 4-O-acetyl-2,3-anhydro-DL-pentopyranosides are reported.

scholarly journals Behaviour Modelling of Organic Bases in the Oxyalkylation Reaction of Proton-Containing Nucleophiles

2018 ◽  
Vol 43 (2) ◽  
pp. 121-135 ◽  
Author(s):  
Stanislav Bakhtin ◽  
Elena Shved ◽  
Yuliia Bespal'ko ◽  
Yuliia Stepanova
Keyword(s):  
Quantum Chemical ◽  
Ring Opening ◽  
Uv Spectroscopy ◽  
Activation Parameters ◽  
Oxirane Ring ◽  
Acetate Anion ◽  
Reactive Intermediate ◽  
Model Base ◽  
Organic Bases ◽  
Initial Base

The mechanism of action of nucleophilic and non-nucleophilic bases in the system “acetic acid (HOAc) – epichlorohydrin (ECH) – R3X (R = alkyl, X = N, P)” has been studied. The observed orders of the reaction with respect to the components were found. It has been proved that the catalytic activity of the starting bases is determined by their nucleophilicity, rather than basicity. It is shown that the crucial stage of the reaction is the quaternisation of the starting base with the formation of a reactive intermediate, the acetate anion. Monitoring of possible paths of oxirane ring-opening by the initial base and the acetate anion was carried out. The behaviour of the model base, triphenylphosphine, in the quaternisation reaction was studied by UV spectroscopy. The rate constants of quaternisation in the reaction of tribenzylamine and triphenylphosphine with ECH have been estimated. The activation parameters of the stages of oxirane ring-opening by trimethylamine and the acetate anion were calculated using a quantum chemical method. It has been shown that the starting base attacks only the activated oxirane, while the acetate anion is capable of nucleophilic opening of both activated and non-activated ECH rings. A scheme for the catalytic opening of the oxirane ring by the bases in the system “ECH – HOAc – R3X” is proposed, which includes a series of both consecutive and parallel stages leading to the formation of the reaction product.

Sign in / Sign up

Export Citation Format

Share Document