Photochemistry of 1,1′-bi-2-naphthol (BINOL) — ESIPT is responsible for photoracemization and photocyclization

2008 ◽  
Vol 86 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Mitchel Flegel ◽  
Matthew Lukeman ◽  
Peter Wan
Keyword(s):  
Intramolecular Proton Transfer ◽  
Deuterium Exchange ◽  
Ring Closure ◽  
The Other ◽  
Quinone Methide ◽  
Direct Result ◽  
Deuterium Incorporation ◽  
Enantiomerically Pure ◽  
Asymmetric Catalysts ◽  
Maximum Quantum Efficiency

The photochemistry of 1,1′-bi-2-naphthol (BINOL, 5) has been studied in aqueous solution and found to undergo rapid deuterium incorporation at the 4 and 5 positions (in D2O-CH3CN). All data is consistent with exchange arising via a formal excited state intramolecular proton transfer (ESIPT) from the naphtholic OH to the 4 and 5 positions of the other ring to give quinine methides (QMs) 8 and 9, respectively, both of which subsequently revert to starting material. Photolysis of enantiomerically pure (+)-5 in D2O-CH3CN resulted in racemization concurrent with deuterium incorporation. This is strong evidence to indicate that photoracemization of BINOL is a direct result of ESIPT, in keeping with the invocation of planar QM intermediates. Prolonged irradiation also gave a ring-closed product that is assigned as dihydrobenzoxanthene 7, based on NMR and UV–vis data, and in analogy to known reactions of similar biaryl systems initiated by ESIPT. The formation of 7 is believed to arise via initial ESIPT from the naphtholic OH to the 7 position of the other naphthol ring generating an o-quinone methide intermediate that subsequently undergoes exclusive electrocyclic ring closure to give 7. The deuterium exchange and photocyclization reach maximum quantum efficiency at ~8 mol/L water (in CH3CN). A “water relay” mechanism for ESIPT is proposed that is consistent with the need for water in the photochemical deuterium exchange, racemization, and formation of 7. The photostability and photoracemization of other related BINOL asymmetric catalysts in water should be a concern based on the reported results herein.Key words: BINOL, ESIPT, photoprotonation, photoracemization, photocyclization, quinone methide.

A study of in-patients aged 60 years and over treated in the Department of Plastic Surgery, Dundee Royal Infirmary, in 1983

1985 ◽  
Vol 71 (3) ◽  
pp. 171-175
Author(s):  
C. D. T. Low
Keyword(s):  
Health Service ◽  
Elderly Patients ◽  
Plastic Surgery ◽  
Special Problem ◽  
The Other ◽  
Special Consideration ◽  
Direct Result ◽  
Royal Infirmary ◽  
Delayed Healing ◽  
Available Resources

SummaryThis study was conducted to determine the extent to which elderly patients constitute a special problem in plastic surgery. In 1983 patients aged 60 years and over accounted for 3 7% of all admissions to the plastic surgery ward at the Dundee Royal Infirmary and 52% of all patient-days there; they tended to stay longer than other patients and cost the Health Service more than £130000. About one-third of admissions were as a direct result of accidents; of the other two-thirds, the majority was for the treatment of malignancies. In the study, special consideration was given to delayed healing after surgery and other problems arising while these patients were in hospital, and the reasons for prolonged stays. The study confirms that there is a problem which is stretching available resources.

scholarly journals Exoticism and East Asian women : moving beyond geishas and dragon ladies

2021 ◽  
Author(s):  
Yuan Mai Elaine Cheong
Keyword(s):  
North America ◽  
East Asian ◽  
The Other ◽  
Direct Result ◽  
Asian Women ◽  
Major Research ◽  
Dominant Culture ◽  
East Asians ◽  
Women's Lives ◽  
Feminist Theories

This major research paper relates my experiences as a Chinese woman to those of other East Asian women while exploring why East Asian women continue to be sexualized and ethnicized. My paper is based on the feminist standpoint and anti-racist feminist theories, and feminist and post-modern methodologies. The focus is on the Chinese immigration experience to North America, and on Chinese women's lives, with some consideration of Korean and Japanese women because the latter two share similarities in experiences of homogenization of East Asian women. I argue that the experiences of every woman are unique because of their race, migration and settlement experiences. I borrow Ang's (2001) term "togetherness in differences" to describe our experiences. The stereotypes of East Asians and East Asian women are not created in a vacuum; rather they are the direct result of the dominant culture oppressing the "other" in the effort to subordinate them.

Solvolysis and ring closure of quinone methides photogenerated from biaryl systems

2005 ◽  
Vol 83 (9) ◽  
pp. 1306-1323 ◽  
Author(s):  
Yijian Shi ◽  
Peter Wan
Keyword(s):  
Ring Closure ◽  
Quinone Methide ◽  
High Yield ◽  
Nanosecond Laser ◽  
Quinone Methides ◽  
Molecular Mechanics Calculations ◽  
Fluorescence Studies ◽  
Long Wavelength ◽  
Thermal Chemistry ◽  
Nanosecond Laser Photolysis

A variety of biaryl quinone methides have been photogenerated with a range of efficiencies from biaryl precursors 4–6 and 8, 10, and 11, all having hydroxyl and hydroxymethyl substituents on alternate rings. These novel biaryl quinone methides, which cannot be readily generated via thermal chemistry, are trapped by added nucleophiles such as MeOH and ethanolamine; two that cannot undergo electrocyclic ring closure (from 8 and 11) are readily observable by nanosecond laser photolysis, with long wavelength maxima (λmax) of 600 and 520 nm, respectively. Photogenerated o,o′-biaryl quinone methides undergo electrocyclic ring closure to give the corresponding chromene (pyran) products in high yield. Since the precursor biaryl alcohols have highly twisted structures in the ground state (dihedral angle of up to 90° by molecular mechanics calculations), a significant twisting motion to planarity is required to achieve reaction. Using steady-state fluorescence studies, we present evidence to suggest that the mechanism of quinone methide formation may occur via one of the following mechanisms: (i) dissociation of the proton from ArOH that precedes twisting; or (ii) ArOH dissociation and twisting taking place either simultaneously or in quick succession.Key words: biaryl quinone methide, photosolvolysis, photodeprotonation, photocyclization.

The Fürstner Synthesis of Amphidinolide F

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Amino Alcohol ◽  
Aldol Condensation ◽  
Free Acid ◽  
The Other ◽  
Unsaturated Ester ◽  
Alkyne Metathesis ◽  
Max Planck ◽  
Ring Closing Metathesis ◽  
Enantiomerically Pure ◽  
Metathesis Catalyst

The amphidinolides, having zero, one, or (as exemplified by amphidinolide F 3) two tetrahydrofuran rings, have shown interesting antineoplastic activity. It is a tribute to his development of robust Mo catalysts for alkyne metathesis that Alois Fürstner of the Max-Planck-Institut für Kohlenforschung Mülheim could with confidence design (Angew. Chem. Int. Ed. 2013, 52, 9534) a route to 3 that relied on the ring-closing metathesis of 1 to 2 very late in the synthesis. Three components were prepared for the assembly of 1. Julia had already reported (J. Organomet. Chem. 1989, 379, 201) the preparation of the E bromodiene 5 from the sulfone 4. The alcohol 7 was available by the opening of the enantiomerically-pure epoxide 6 with propynyl lithium, followed by oxidation following the Pagenkopf pro­tocol. Amino alcohol-directed addition of the organozinc derived from 5 to the alde­hyde from oxidation of 7 completed the assembly of 8. Addition of the enantiomer 10 of the Marshall butynyl reagent to 9 followed by protection, oxidation to 11, and addition of, conveniently, the other Marshall enan­tiomer 12 led to the protected diol 13. Silylcupration–methylation of the free alkyne set the stage for selective desilylation and methylation of the other alkyne. Iodination then completed the trisubstituted alkene of 14. Methylation of the crystalline lactone 15, readily prepared from D-glutamic acid, led to a mixture of diastereomers. Deprotonation of that product followed by an aque­ous quench delivered 16. Reduction followed by reaction with the phosphorane 17 gave the unsaturated ester, that cyclized with TBAF to the crystalline 18. The last ste­reogenic center of 22 was established by proline-mediated aldol condensation of the aldehyde 19 with the ketone 20. To assemble the three fragments, the ketone of 21 was converted to the enol triflate and thence to the alkenyl stannane. Saponification gave the free acid 22, that was acti­vated, then esterified with the alcohol 18. Coupling of the stannane with the iodide 14 followed by removal of the TES group led to the desired diyne 1. It is noteworthy that the Mo metathesis catalyst is stable enough to tolerate the free alcohol of 1 in the cyclization to 2.

Credibility in Sustainable Aquaculture Eco-Labeling

2019 ◽  
pp. 81-116
Author(s):  
Hamish van der Ven
Keyword(s):  
Best Practice ◽  
Geographic Location ◽  
Poor Performance ◽  
The Other ◽  
Process Tracing ◽  
Direct Result ◽  
Sustainable Aquaculture ◽  
Origin And Evolution ◽  
Domestic Markets ◽  
Comparative Case Studies

This chapter tests the aiming big hypothesis by tracing the origin and evolution of four eco-labeling organizations in sustainable aquaculture: the Aquaculture Stewardship Council (ASC), Best Aquaculture Practices (BAP), Friend of the Sea (FOS), and Naturland. The chapter argues that stronger adherence to best practices in the ASC and BAP programs is a direct result of their decision to target large multinational retailers for certification. Conversely, the comparatively poor performance of the other two eco-labeling organizations can be traced to their decisions to target smaller firms in domestic markets. The chapter uses comparative case studies and within-case process tracing to reveal how decisions about who to target for certification impacted best practice adherence through the causal mechanisms outlined in chapter 3. The four cases analyzed in this chapter cast further doubt on alternate theories of credibility, such as the relevance of ownership or geographic location to credibility.

Synthesis of indenofurans, benzofurans and spiro-lactones via Hauser–Kraus annulation involving 1,6-addition of phthalide to quinone methides

2020 ◽  
Vol 18 (29) ◽  
pp. 5677-5687
Author(s):  
Pallabita Basu ◽  
Nishikant Satam ◽  
Irishi N. N. Namboothiri
Keyword(s):  
Ring Opening ◽  
Ring Closure ◽  
Quinone Methide ◽  
Quinone Methides ◽  
Oxygen Heterocycles ◽  
Multiple Ring

Base mediated 1,6-addition–Dieckmann cyclization of phthalide with quinone methide leads to oxygen heterocycles such as indenofurans, spiro-lactones and benzofurans through a cascade of rearrangements involving multiple ring opening and ring closure.

scholarly journals Regioselective and Stereodivergent Synthesis of Enantiomerically Pure Vic-Diamines from Chiral β-Amino Alcohols with 2-Pyridyl and 6-(2,2′-Bipyridyl) Moieties

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 727 ◽  
Author(s):  
Marzena Wosińska-Hrydczuk ◽  
Przemysław J. Boratyński ◽  
Jacek Skarżewski
Keyword(s):  
Ring Opening ◽  
Amino Alcohols ◽  
Ring Closure ◽  
Mitsunobu Reaction ◽  
Hydroxyl Group ◽  
Hydrazoic Acid ◽  
Enantiomerically Pure ◽  
Endocyclic Nitrogen Atom ◽  
Diastereomeric Mixture ◽  
Complete Series

In this report, we describe the synthetic elaboration of the easily available enantiomerically pure β-amino alcohols. Attempted direct substitution of the hydroxyl group by azido-functionality in the Mitsunobu reaction with hydrazoic acid was inefficient or led to a diastereomeric mixture. These outcomes resulted from the participation of aziridines. Intentionally performed internal Mitsunobu reaction of β-amino alcohols gave eight chiral aziridines in 45–82% yield. The structural and configuration identity of products was confirmed by NMR data compared to the DFT calculated GIAO values. For 1,2,3-trisubstituted aziridines slow configurational inversion at the endocyclic nitrogen atom was observed by NMR at room temperature. Moreover, when aziridine was titrated with Zn(OAc)2 under NMR control, only one of two N-epimers directly participated in complexation. The aziridines underwent ring opening with HN3 to form the corresponding azido amines as single regio- and diastereomers in 90–97% yield. Different results were obtained for 1,2-disubstituted and 1,2,3-trisubstituted aziridines. For the later aziridines ring closure and ring opening occurred at different carbon stereocenters, thus yielding products with two inverted configurations, compared to the starting amino alcohol. The 1,2-disubstituted aziridines produced azido amines of the same configuration as the starting β-amino alcohols. To obtain a complete series of diastereomeric vic-diamines, we converted the amino alcohols into cyclic sulfamidates, which reacted with sodium azide in SN2 reaction (25–58% overall yield). The azides obtained either way underwent the Staudinger reduction, giving a series of six new chiral vic-diamines of defined stereochemistries.

The Politics of Anti-Bolshevism: the French Government and the Russo-Polish War, December 1919 to May 1920

1976 ◽  
Vol 19 (1) ◽  
pp. 163-189 ◽  
Author(s):  
Michael Jabara Carley
Keyword(s):  
Full Scale ◽  
The Other ◽  
Detailed Account ◽  
Direct Result ◽  
Left Wing ◽  
French Government ◽  
Other Hand ◽  
Soviet Russia

On 26 April 1920 the Polish army launched a major offensive against Soviet Russia. The question of the French government's role in the unleashing of this attack has long been a matter of historical debate. P. S. Wandycz, whose work is the most recent detailed account of French eastern policy during the early twenties, attributes no major responsibility to the French for the outbreak of all-out war on Poland's eastern frontier. He states that the Quai d'Orsay was unenthusiastic about a Polish campaign and that the Poles had acted on their own initiative. N. Davies asserts that ‘Allied policy sought to discourage Poland from attacking Russia.’ ‘Without formally forbidding a Polish offensive,’ he writes, the Allies ‘emphasized that it “the offensive’ could not enjoy their support. On the other hand, Soviet and European Left-wing opinion has long condemned the Polish attack as a direct result of French influence. Vladimir Potemkin noted that Poland was incapable of waging a full-scale war with its own resources and that consequently Allied influence had to be decisive in determining Warsaw's attitude toward a continuation of the war.

scholarly journals Synthesis and Structural Elucidation of the Acetylation Reaction’s Product(s) of the 2(1H)-Quinoxalinones Derived from L-Ascorbic Acid. X-Ray Molecular Structure of 3-(N-acetyl-2-naphthylhydrazono)-2,3-dihydro-2-acetoxyfuro[2,3-b]quinoxaline [1]

1992 ◽  
Vol 47 (6) ◽  
pp. 861-868 ◽  
Author(s):  
Adel Amer ◽  
Douglas M. Ho
Keyword(s):  
Molecular Structure ◽  
Ascorbic Acid ◽  
Acetic Anhydride ◽  
Structural Elucidation ◽  
Ring Closure ◽  
The Other ◽  
High Yield ◽  
X Ray ◽  
Reaction Condition ◽  
Tricyclic Compound

Acetylation reaction’s product(s) of 3-[L-threo-2,3,4-trihydroxy-1-(2-naphthylhydrazono)-butyl]quinoxalin-2(1H)-one (2b) were found to be dependent on the reaction condition. While the tri-O-acetyl (3b) was isolated in high yield from 2b under the action of acetic anhydride/pyridine mixture, compounds 4b and 5b as well as trace of 3b were obtained when 2b was heated in acetic anhydride. On the other hand, 3-[1-(2-naphthylhydrazono)-glyoxal-1-yl]quinoxalin-2(1H)-one (7) underwent ring closure and afforded the condensed tricyclic compound 8 under the action of acetic anhydride/pyridine mixture.

Residential Satisfaction, Neighbourhood Attributes, and Personal Characteristics: An Exploratory Path Analysis in Cork, Ireland

1984 ◽  
Vol 16 (4) ◽  
pp. 425-436 ◽  
Author(s):  
K Hourihan
Keyword(s):  
Path Analysis ◽  
Personal Characteristics ◽  
Residential Satisfaction ◽  
The Other ◽  
Direct Result ◽  
Neighbourhood Satisfaction ◽  
Personal Variables

Many studies of residential satisfaction have shown that the effect of residents' personal characteristics is mediated through their perceptions and evaluations of attributes of their neighbourhoods, but have not been able to show how this occurs. A path analysis which treats the personal variables as causally antecedent was tested in Cork, Ireland. This shows neighbourhood satisfaction to be a direct result of four perceived attributes and two personal characteristics, which together explain 38% of the variation in satisfaction. The other personal variables are mediated through these direct causes and contribute indirectly to satisfaction levels.

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