Photocyclization of Coumarinoyl Enamides Revisited: [2+2+2]Cycloreversion/Cycloaddition Mechanism

2021 ◽  
Author(s):  
Sivanna Chithanna ◽  
Ding-Yah Yang
Keyword(s):  
Minor Isomer

The major and minor products for photocyclization of coumarinoyl enamides were identified. The controlled and intermediate-trapping experiments indicate that the formation of the minor isomer involved a stepwise, radical [2+2+2]...

(Invited) Separation and Photophysical Properties of C 84 Minor Isomer D 2d (I)

2017 ◽  
Vol 77 (11) ◽  
pp. 581-588
Author(s):  
Eric Booth ◽  
Sanichiro Yoshida ◽  
Yao Jin ◽  
Mandy Mitchell ◽  
Ju Chou
Keyword(s):  
Photophysical Properties ◽  
Minor Isomer

B31− and B32−: chiral quasi-planar boron clusters

Nanoscale ◽  
2019 ◽  
Vol 11 (19) ◽  
pp. 9698-9704 ◽  
Author(s):  
Qiang Chen ◽  
Teng-Teng Chen ◽  
Hai-Ru Li ◽  
Xiao-Yun Zhao ◽  
Wei-Jia Chen ◽  
...  
Keyword(s):  
Theoretical Investigation ◽  
Minor Isomer ◽  
Boron Clusters ◽  
A Minor

Chiral boat-like B31− (C1, I and II) and B32− (C2, VI and VII) are characterized in a joint experimental and theoretical investigation, with a chair-like intermediate (Ci, VIII) also observed for B32− as a minor isomer.

Formation and reactivity of the zirconium ethylene complexes [η5-C5H3-1,3-(SiMe2CH2PR2)2]Zr(η2-CH2=CH2)(X) (R = Me, Pr i; X = Br, C5H5)

2001 ◽  
Vol 79 (5-6) ◽  
pp. 536-545 ◽  
Author(s):  
Michael D Fryzuk ◽  
Paul B Duval ◽  
Steven J Rettig
Keyword(s):  
Carbon Monoxide ◽  
Solid State ◽  
Kinetic Parameters ◽  
Structure Determination ◽  
Exchange Process ◽  
Carbonyl Complex ◽  
Carbonyl Ligand ◽  
Minor Isomer ◽  
X Ray ◽  
X Ray Crystallography

The formation and reactivity of the zirconium ethylene complexes R[P2Cp]Zr(η2-CH2=CH2)(X) (2a: R = Pri, X = Br; 2b: R = Me, X = Br; 4a: R = Pri, X = C5H5; R[P2Cp] = (η5-C5H3-1,3-(SiMe2CH2PR2)2)) are described. Ethylene complexes 2a and 2b are prepared from a reaction of R[P2Cp]ZrCl3 (1a: R = Pri; 1b: R = Me) with 2 equiv of EtMgBr, presumably via β-H elimination from the diethyl intermediate R[P2Cp]ZrCl(CH2CH3)2. The structure of 2b was determined by X-ray crystallography. Addition of carbon monoxide to 16-electron 2 displaces the ethylene ligand to generate the carbonyl complex R[P2Cp]Zr(CO)2Br (5a: R = Pri; 5b: R = Me), which is stable only under an atmosphere of CO. The corresponding CO reaction with 18-electron 4a to give the metallocene monocarbonyl analogue Pr[P2Cp]Zr(η5-C5H5)(CO) (6a) is considerably slower. 2a exhibits fluxional exchange of one carbonyl ligand with bulk 13CO in solution; the kinetic parameters for this exchange process are ΔH ‡ = 9.2(5) kcal mol–1 and ΔS ‡ = –17(2) cal mol–1 K–1. The addition of diphenylacetylene to 2a yields the alkyne complex Pr[P2Cp]Zr(η2-PhCCPh)Br (7a), which exists in solution as two isomers in equilibrium. A solid-state X-ray structure determination for the minor isomer syn-7a was performed.Key words: zirconium, cyclopentadienyl phosphine, alkyne, metallocyclopropane.

Synthesis of (E,Z)-α-,(Z,Z)-α-, and (Z)-β-farnesene

1970 ◽  
Vol 23 (10) ◽  
pp. 2101 ◽  
Author(s):  
EFLJ Anet
Keyword(s):  
Mass Spectra ◽  
Phosphoryl Chloride ◽  
Minor Isomer ◽  
Liquid Phases

The three farnesenes (E,Z)-or-, (Z,Z)-or-, and (2)-P- were synthesized from (cis) (2)-nerolidol by dehydration with phosphoryl chloride in pyridine. The i.r., u.v., N.M.R., and mass spectra of the six possible α- and β-farnesenes are compared as well as their behaviour on g.1.c. on several liquid phases. The α-farnesene which predominates in apples was confirmed as being (E,E)-α-farnesene and the minor isomer, previously thought to be (E,Z)-α-farnesene, was shown to be (Z,E)-α- farnesene.

Isobenzofulvenes. VIII. The structure of the dimers derived from 8,8-dimethylisobenzofulvene. A PMO treatment of the perispecificity in this dimerization and related cycloadditions involving isobenzofulvenes

1981 ◽  
Vol 34 (2) ◽  
pp. 397 ◽  
Author(s):  
RN Warrener ◽  
MN Paddon-Row ◽  
RA Russell ◽  
PL Watson
Keyword(s):  
Transition State ◽  
Structure Analysis ◽  
Chemical Degradation ◽  
Minor Isomer ◽  
X Ray ◽  
Firm Basis ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents

8,8-Dimethylisobenzofulvene, generated from the reaction of ll-isopropylidenetricyclo[6,2,1,02.7]- undeca-2,4,6,9-tetraene (23) and 3,6-di(pyridin-2-yl)-s-tetrazine, undergoes spontaneous dimerization to form a mixture of two isomers. This is shown to be a mixture of endo (33) and exo isomers (37) resulting from [π10s+π8s] cyclodimerization, with the former isomer predominating. 1H and 13C n.m.r. spectroscopy, in conjunction with lanthanide shift reagents and spin decoupling, was used, together with chemical degradation, to determine the structure and stereochemistry of these products. Chemical interconversion has placed these structures on a firm basis since the structure of the minor isomer has been determined by X-ray structure analysis. The constancy of this dimer ratio in solvents of widely differing polarity, and in the absence of solvent, supports an isopolar transition state which is typical of many concerted electrocyclic processes. A complete PMO treatment of all possible modes of isobenzofulvene dimerization is presented and the results of these calculations are discussed in terms of the observed peri- and stereospecificities. In a similar way, the PMO model is successfully employed to explain the relative efficiencies of various polyenophiles in trapping the isobenzofulvene nucleus.

Preferred location of the Dy ion in the minor isomer of Dy@C82 determined by Dy LIII-edge EXAFS

2004 ◽  
Vol 388 (1-3) ◽  
pp. 23-26 ◽  
Author(s):  
Y Takabayashi ◽  
Y Haruyama ◽  
Y Rikiishi ◽  
T Hosokawa ◽  
K Shibata ◽  
...  
Keyword(s):  
Minor Isomer
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