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.

Metal hydride reductions of unsymmetrical cyclic anhydrides. The importance of the antiperiplanar effect on the regioselectivity of these reactions

1982 ◽  
Vol 60 (10) ◽  
pp. 1192-1198 ◽  
Author(s):  
Margaret M. Kayser ◽  
Georges Wipff
Keyword(s):  
Carbonyl Group ◽  
Metal Hydride ◽  
Lower Energy ◽  
Succinic Anhydride ◽  
Chair Conformation ◽  
Nucleophilic Attack ◽  
Quantum Mechanical ◽  
Mechanical Study ◽  
Quantum Mechanical Study ◽  
Experimental Findings

A quantum mechanical study by the SCF abinitio method of the interaction of H− with methylsuccinic and 2,2-dimethylsuccinic anhydrides (naked and in the presence of a cation) suggests that nonperpendicular rearside attack cannot be the factor responsible for the regioselectivity of hydride transfer to the more sterically hindered carbonyl group. In this model, the nucleophilic attack at the less hindered carbonyl group is calculated to be of lower energy (with or without cation). Deformation of the planar succinic anhydride ring to the quasi-chair conformation is energetically favoured as it allows the nucleophile to attack both carbonyl functions antiperiplanar to a quasi axial C—H or C—C bond. The attack antiperiplanar to the C—CH3 bond is lower in energy than the attack antiperiplanar to the C—H bond suggesting that the reduction will occur at the sterically more hindered carbonyl group which is in agreement with the experimental findings.

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.

Regioselectivity of metal hydride reductions of unsymmetrically substituted cyclic anhydrides. systems where "steric hindrance along the preferred reaction path" rationalization is not applicable

1980 ◽  
Vol 58 (23) ◽  
pp. 2484-2490 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Transition State ◽  
Metal Hydride ◽  
Reaction Path ◽  
Steric Effects ◽  
Carbonyl Groups ◽  
Qualitative Interpretation ◽  
Alkaline Cation ◽  
Cyclic Anhydrides ◽  
Late Transition ◽  
Carbonyl Function

Metal hydride reductions of planar cyclic anhydrides such as methylmaleic or 3-substituted phthalic anhydrides occur preferentially at the sterically more hindered carbonyl function. This regioselectivity cannot be rationalized in terms of "the most favourable pathway for non-perpendicular attack by a nucleophile" since both carbonyl groups present are equally accessible to non-perpendicular approach. A study which takes into account the alkaline cation and inductive, mesomeric, and steric effects has been conducted for the reduction of several conjugated and aromatic anhydrides. A qualitative interprétation for the regioselectivities observed in these reductions (as well as in reductions already reported in the literature) is suggested. An early transition state for the catalyzed versus late transition state for the non-catalyzed process is proposed.

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.

Customer’s satisfaction on service quality at Vietnam Technological and Commercial Joint Stock Bank – An Giang Branch

2020 ◽  
Vol 4 (3) ◽  
pp. First
Author(s):  
Tran Minh Hieu ◽  
Nguyen Duong Ngoc Mai Chi
Keyword(s):  
Customer Satisfaction ◽  
Service Quality ◽  
Test Method ◽  
Quality Of Services ◽  
Factors Affecting ◽  
Factors Influencing ◽  
Alpha Reliability ◽  
Survey Results ◽  
Development Orientation

This study applied SERVQUAL scale of Parasuraman et al to measure factors affecting customer satisfaction on service quality at Vietnam Technological and Commercial Joint Stock Bank - An Giang Branch (Techcombank An Giang). The study was conducted to survey 207 customers who have been using the service at Techcombank An Giang. The survey results were analyzed by the Cronbach's Alpha reliability test method, then used Exploratory factor analysis (EFA) to verify and evaluate the scale of service quality. The results of the regression analysis show that customer's satisfaction about service quality at Techcombank An Giang includes four factors: The factor with the highest level is the Empathy with Beta = 0.253, the second of factor is the Responsibility with Beta = 0.248, ranked third in the influence level is the Tangible with Beta = 0.235, and the lowest impact level is the Reliability with Beta = 0.144. The research also uses statistical methods to describe and test the differences of demographic factors with customer's satisfactionon service quality.The analysis results show that there is no difference between customer's satisfaction on service quality and factors such as gender, age, income, number of transaction banks, regular transaction banks, and time to use the service at Techcombank An Giang. Through the research results, the author would like to propose some ideas to improve the quality of services, thereby attracting new customers and importantly, keeping traditional customers because the development orientation of Techcombank is to take care of old customers to cross sell other products of the bank. The Stud results offer a basis for the branch to identify the factors influencing customer satisfaction on their service quality, thereby having an appropriate strategy to improve customer satisfaction.

Factors Influencing Utilisation of Maternal Healthcare Services: Womens Perception

2015 ◽  
Vol 4 (1and2) ◽  
Author(s):  
Gyanvati
Keyword(s):  
Healthcare Services ◽  
Maternal Healthcare ◽  
Factors Affecting ◽  
Factors Influencing ◽  
Economic Background ◽  
Newborn Child

This paper analyses the factors affecting for utilization of maternal healthcare services. Following is the section wise description of the paper. Firstly, the paper looks into socio-economic background of women. Secondly, the paper focuses on usage of maternal healthcare services by women. Thirdly, the paper also traces the factors affecting for usage of maternal healthcare services. Lastly, the paper concludes and suggests by emphasizing the significance of proper utilization of maternal healthcare services that it leads to better health of mother and their newborn child.

Assessment of factors affecting short-term pulmonary functions following cardiac surgery: A prospective observational study

2021 ◽  
pp. 021849232110100
Author(s):  
Neetika Katiyar ◽  
Sandeep Negi ◽  
Sunder Lal Negi ◽  
Goverdhan Dutt Puri ◽  
Shyam Kumar Singh Thingnam
Keyword(s):  
Cardiac Surgery ◽  
Pulmonary Function ◽  
Forced Vital Capacity ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Pulmonary Complications ◽  
Operative Morbidity ◽  
Factors Affecting ◽  
Factors Influencing ◽  
Significant Impairment

Background Pulmonary complications after cardiac surgery are very common and lead to an increased incidence of post-operative morbidity and mortality. Several factors, either modifiable or non-modifiable, may contribute to the associated unfavorable consequences related to pulmonary function. This study was aimed to investigate the degree of alteration and factors influencing pulmonary function (forced expiratory volume in one second (FEV1) and forced vital capacity), on third, fifth, and seventh post-operative days following cardiac surgery. Methods This study was executed in 71 patients who underwent on-pump cardiac surgery. Pulmonary function was assessed before surgery and on the third, fifth, and seventh post-operative days. Data including surgical details, information about risk factors, and assessment of pulmonary function were obtained. Results The FEV1 and forced vital capacity were significantly impaired on post-operative days 3, 5, and 7 compared to pre-operative values. The reduction in FEV1 was 41%, 29%, and 16% and in forced vital capacity was 42%, 29%, and 19% consecutively on post-operative days 3, 5, and 7. Multivariate analysis was done to detect the factors influencing post-operative FEV1 and forced vital capacity. Discussion This study observed a significant impairment in FEV1 and forced vital capacity, which did not completely recover by the seventh post-operative day. Different factors affecting post-operative FEV1 and forced vital capacity were pre-operative FEV1, age ≥60, less body surface area, lower pre-operative chest expansion at the axillary level, and having more duration of cardiopulmonary bypass during surgery. Presence of these factors enhances the chance of developing post-operative pulmonary complications.

scholarly journals Electronic and steric factors affecting ligand binding: horse hemoglobins containing 2,4-dimethyldeuteroheme and 2,4-dibromodeuteroheme.

1977 ◽  
Vol 252 (12) ◽  
pp. 4225-4231 ◽  
Author(s):  
D W Seybert ◽  
K Moffat ◽  
Q H Gibson ◽  
C K Chang
Keyword(s):  
Ligand Binding ◽  
Factors Affecting ◽  
Steric Factors
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