ChemInform Abstract: REDUCTION OF CYCLIC ANHYDRIDES. II. FACTORS AFFECTING REGIOSELECTIVITY OF ATTACK ON THE CARBONYL GROUP BY METAL HYDRIDES

1978 ◽  
Vol 9 (40) ◽  
Author(s):  
M. M. KAYSER ◽  
P. MORAND
Keyword(s):  
Carbonyl Group ◽  
Metal Hydrides ◽  
Factors Affecting ◽  
Cyclic Anhydrides

Reduction of cyclic anhydrides. II. Factors affecting regioselectivity of attack on the carbonyl group by metal hydrides

1978 ◽  
Vol 56 (11) ◽  
pp. 1524-1532 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Carbonyl Group ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Factors Affecting ◽  
Preferential Formation ◽  
Factors Influencing ◽  
Steric Factors ◽  
Cyclic Anhydrides ◽  
Experimental Findings ◽  
Carbonyl Function

The reduction of unsymmetrically substituted cyclic anhydrides with metal hydrides often leads to the preferential formation of one of the two possible lactones. In the light of recent experimental findings and theories concerning metal hydride addition to the carbonyl function, the electronic and steric factors influencing regioselectivity of cyclic anhydride reductions are discussed and an explanation for the observed patterns is proffered. Similar considerations may be extended to predict the major lactonic products in the reductions of various other unsymmetrical cyclic anhydrides.

scholarly journals Investigating the Factors Affecting the Ionic Conduction in Nanoconfined NaBH4

Inorganics ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 2
Author(s):  
Xiaoxuan Luo ◽  
Aditya Rawal ◽  
Kondo-Francois Aguey-Zinsou
Keyword(s):  
Ionic Conductivity ◽  
Ionic Conduction ◽  
Metal Hydrides ◽  
Ionic Conductivities ◽  
Effective Strategy ◽  
Li Ion Batteries ◽  
Large Cage ◽  
Factors Affecting ◽  
Li Ion ◽  
Mcm 41

Nanoconfinement is an effective strategy to tune the properties of the metal hydrides. It has been extensively employed to modify the ionic conductivity of LiBH4 as an electrolyte for Li-ion batteries. However, the approach does not seem to be applicable to other borohydrides such as NaBH4, which is found to reach a limited improvement in ionic conductivity of 10−7 S cm−1 at 115 °C upon nanoconfinement in Mobil Composition of Matter No. 41 (MCM-41) instead of 10−8 S cm−1. In comparison, introducing large cage anions in the form of Na2B12H12 naturally formed upon the nanoconfinement of NaBH4 was found to be more effective in leading to higher ionic conductivities of 10−4 S cm−1 at 110 °C.

Methylsteroids. VII. Factors Affecting the Hydrolysis of 7α- and 11β-Acetoxylanostanes

1961 ◽  
Vol 14 (1) ◽  
pp. 48
Author(s):  
CS Barnes ◽  
BD Beilby
Keyword(s):  
Carbonyl Group ◽  
Carbonyl Groups ◽  
Factors Affecting ◽  
Steric Crowding ◽  
Methylene Groups ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Methylene Group

Doubly bonded methylene groups have been introduced into 7α- and 11β-acetoxylanostanes and the rate of hydrolysis compared with compounds having a hydroxy or carbonyl group at the same position as the methylene group. It was found that methylene groups facilitate hydrolysis of the hindered acetoxy groups in the same way, but not to the same extent, as carbonyl groups. It is concluded that the facilitation in each case results from a conformational disturbance, but that there is some other factor involved in carbonyl facilitation. It was not possible to demonstrate a similar effect resulting from steric crowding of substituents.

Changing regioselectivity patterns in metal hydride reductions of unsymmetrically substituted cyclic anhydrides

1983 ◽  
Vol 61 (3) ◽  
pp. 439-441 ◽  
Author(s):  
Margaret M. Kayser ◽  
Judith Salvador ◽  
Peter Morand
Keyword(s):  
Carbonyl Group ◽  
Metal Hydride ◽  
Nucleophilic Additions ◽  
Substrate Molecule ◽  
Parent Molecule ◽  
Cyclic Anhydrides ◽  
Intrinsic Reactivity

A study of L- and K-selectride reductions of unsymmetrical cyclic anhydrides attached to six-membered rings and to bridged six-membered systems sheds a new light on the effect of the conformation of the substrate molecule on the regioselectivity of metal hydride reductions. Thus, in addition to intrinsic reactivity of the carbonyl group, the antiperiplanar effect, and steric congestion, the conformation of the parent molecule should be considered in predicting regioselectivity of nucleophilic additions to cyclic anhydrides.

Theoretical study of regioselectivity in nucleophilic addition to unsymmetrical cyclic anhydrides. Intrinsic reactivity and influence of the cation

1981 ◽  
Vol 59 (16) ◽  
pp. 2457-2462 ◽  
Author(s):  
Margaret M. Kayser ◽  
Odile Eisenstein
Keyword(s):  
Carbonyl Group ◽  
Nucleophilic Addition ◽  
Nucleophilic Attack ◽  
Dominant Factor ◽  
Molecular Orbital Calculations ◽  
Optimum Position ◽  
Cyclic Anhydrides ◽  
Intrinsic Reactivity ◽  
Reaction Media ◽  
Phthalic Anhydrides

Ab initio molecular orbital calculations have been carried out for the series of succinic, maleic, and phthalic anhydrides unsymmetrically substituted with CH3, CH3O, Cl, F, and CN. The size of the LUMO coefficient on the carbon atom of the carbonyl group provides a reliable guide to the relative reactivities of the two carbonyl functions. The predictions based on the intrinsic reactivities are in good agreement with the regioselectivities observed in metal hydride reductions of succinic anhydrides. In the series of maleic and phthalic anhydrides the above considerations are applicable only to methyl derivatives. The compounds substituted with lone pairs-bearing groups (OCH3, Cl, F) form stable chelates with the cations present in the reaction media. Since the chelated carbonyl group is strongly activated toward the nucleophilic addition, the "bridging" effect is the dominant factor controlling orientation of hydride addition. The optimum position for the nucleophilic attack in cyclic anhydrides was calculated. The results confirm the generality of the nonperpendicular, restricted path of nucleophilic attack on the carbonyl group in succinic anhydride.

On the regioselectivity of Wittig reactions with unsymmetrically substituted succinic anhydrides

1989 ◽  
Vol 67 (9) ◽  
pp. 1401-1410 ◽  
Author(s):  
Margaret M. Kayser ◽  
Livain Breau
Keyword(s):  
Oxygen Atom ◽  
Transition State ◽  
Carbonyl Group ◽  
Wittig Reaction ◽  
Cyclic Anhydrides ◽  
Wittig Reactions ◽  
Deficient Phosphorus

Phosphorane ylids react readily with succinic anhydrides to give enol-lactones. With highly substituted succinic anhydrides, condensations occur at the less substituted carbonyl group, suggesting that the reaction is sterically controlled. This, however, is not the case in monosubstituted anhydrides where effects other than steric become dominant. Condensation of phosphorane 1a with methoxysuccinic anhydride occurs selectively at the carbonyl group adjacent to the substituent. Stabilization of the transition state through complexation between the oxygen atom of the substituent and an electron-deficient phosphorus of the ylid is proposed. Keywords: cyclic anhydrides, Wittig reaction, regioselectivity, stabilized ylid.

Metal hydride reductions of unsymmetrically substituted cyclic anhydrides attached to strained ring systems

1982 ◽  
Vol 60 (10) ◽  
pp. 1199-1206 ◽  
Author(s):  
Margaret M. Kayser ◽  
Judith Salvador ◽  
Peter Morand ◽  
H. G. Krishnamurty
Keyword(s):  
Carbonyl Group ◽  
Metal Hydride ◽  
Theoretical Calculations ◽  
Ring Systems ◽  
Hydride Reduction ◽  
Cyclic Anhydrides ◽  
Intrinsic Reactivity

A dramatic reversal in regioselectivity is observed in the metal hydride reduction of unsymmetrical cyclic anhydrides such as 2,3, and 4 compared to cyclic anhydrides attached to bridged ring systems (e.g. 1). The synthesis of model cyclic anhydrides attached to strained rings is described and the ratios of isomeric lactones obtained upon reduction with metal hydride are reported. On the basis of theoretical calculations and, taking into account the intrinsic reactivity of the carbonyl group, the antiperiplanar effect, and steric congestion, an explanation is offered for the regioselectivity observed in the reduction of these compounds.

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