Reactions of 2-phenyl-4H-1,3,2-benzodioxaborin, a stable ortho-quinone methide precursor

1992 ◽  
Vol 70 (6) ◽  
pp. 1717-1732 ◽  
Author(s):  
Jeffrey D. Chambers ◽  
Jason Crawford ◽  
Haydn W. R. Williams ◽  
Claude Dufresne ◽  
John Scheigetz ◽  
...  
Keyword(s):  
Vinyl Ether ◽  
Lewis Acid ◽  
Quinone Methide ◽  
Ethyl Vinyl Ether ◽  
Cycloaddition Reactions ◽  
Substituted Phenols ◽  
Quinone Methides ◽  
Ethyl Vinyl ◽  
Aryl Group ◽  
Intramolecular Reaction

Thermolysis of 1-phenyl-4H-1,3,2-benzodioxaborins generated the corresponding ortho-quinone methides, which were found to undergo intermolecular cycloaddition reactions with ethyl vinyl ether, dihydropyran, β-methylstyrene, cyclohexene, and 1-ethoxy-1-z-trimethylsiloxy-1-propenes to give various substituted chromans. Intramolecular trapping of the quinone methides with an olefin led to the syntheses of several analogs of tetrahydrocannabinols. ortho-Quinone methides, generated by treatment of the 2-phenyl-4H-1,3,2-benzodioxaborins with a Lewis acid, react with various nucleophiles to give the corresponding 1,4-addition products. Thus, alkyl and aryl thiols, alcohols, amine, hydride, allyl trimethylsilane, acetophenone, and diethylmalonate as well as some aryl compounds react with the quinone methide to give various 2-substituted phenols. Intramolecular reaction of the quinone methide with an aryl group led to the preparation of some 4-phenylchromans and tetralins.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 868-874
Author(s):  
Maike Fischer ◽  
Yijian Shi ◽  
Bao-ping Zhao ◽  
Victor Snieckus ◽  
Peter Wan
Keyword(s):  
Aqueous Solution ◽  
Vinyl Ether ◽  
Hydroxy Group ◽  
Ground State ◽  
Cycloaddition Reaction ◽  
Quinone Methide ◽  
Quantum Yields ◽  
Ethyl Vinyl Ether ◽  
High Chemical ◽  
Ethyl Vinyl

The photosolvolysis of 1- and 2-hydroxy-9-fluorenols 4-6 has been studied in aqueous solution. All of these 9-fluorenols photosolvolyze efficiently in 1:1 H2O-CH3OH, to give the corresponding methyl ether products in high chemical and quantum yields. Whereas the photosolvolysis of the parent 9-fluorenol (2, R = H) is known to proceed via the very short-lived and formally ground-state antiaromatic 9-fluorenyl cation (1, R = H), the photosolvolysis of 1-hydroxy-9-fluorenol (4) proceeds via a much longer-lived (approximately = 5-10 s) fluorenyl quinone methide 9, which is trappable by ethyl vinyl ether via a [4+2] cycloaddition reaction to give a chroman derivative. Interestingly, 2-hydroxy-9-fluorenol (5) photosolvolyzes via a very short-lived intermediate with similar lifetimes as observed for the 9-fluorenyl cation (1, R = H), although a corresponding fluorenyl quinone methide intermediate is accessible for this compound. This study demonstrates that the mechanism of photosolvolysis of these types of compounds can be dramatically altered when an aryl hydroxy group is present.Key words: photosolvolysis, 9-fluorenyl cation, quinone methide, carbocation, antiaromatic.

Cycloaddition Reactions of Arylmethylenemalonaldehydes with Olefins

1992 ◽  
Vol 57 (11) ◽  
pp. 2337-2358 ◽  
Author(s):  
Dalimil Dvořák ◽  
David Šaman ◽  
Zdeněk Arnold ◽  
Ivana Císařová ◽  
Václav Petříček
Keyword(s):  
Nmr Spectroscopy ◽  
Carboxylic Acid ◽  
Vinyl Ether ◽  
Aromatic Nucleus ◽  
Ethyl Vinyl Ether ◽  
Cycloaddition Reactions ◽  
Ethyl Vinyl ◽  
X Ray ◽  
H Nmr ◽  
Conformational Equilibria

A series of 2,4-disubstituted 3,4-dihydro-2H-pyran-5-carboxaldehydes II-XIX was prepared by reaction of substituted arylmethylenemalonaldehydes I with 2-methylpropane, 1,1-diphenylethylene, styrene, ethyl vinyl ether, 1,1-dimethoxyethylene and 1,1-bis(methylthio)ethylene. In the case of the reaction with ethyl vinyl ether the dependence of the ratio of the arising cis- and trans- 2-ethoxy-4-aryl-3,4-dihydropyran-5-carboxaldehydes VII-XIV on the substitutent on the aromatic nucleus was studied. Information on the mechanism of this reaction was obtained and conformational equilibria of 2-ethoxy-4-aryl-3,4-dihydropyran-5-carboxaldehydes in solution were studied by 1H NMR spectroscopy. The structure of trans-2-ethoxy-4-(4-chlorophenyl)-3,4-dihydropyran-5-carboxaldehyde (trans-VIII) was confirmed by X-ray analysis of the corresponding carboxylic acid trans-XXII.

Computational Study on the Mechanism of Cycloaddition Reactions of Bissulfonyl-1,3-butadiene with Some Alkenes

2020 ◽  
Vol 17 (10) ◽  
pp. 735-742
Author(s):  
Sepideh Masoumifar ◽  
Mina Haghdadi ◽  
Hassan Ghasemnejad Bosra
Keyword(s):  
Vinyl Ether ◽  
Energy Barrier ◽  
Computational Study ◽  
Cycloaddition Reaction ◽  
Dft Method ◽  
Ethyl Vinyl Ether ◽  
Cycloaddition Reactions ◽  
Ethyl Vinyl

The cycloaddition reactions of 2,3-bis (ethylene sulfonyl)-1,3-butadiene with 2,3-dimethyl- 1,3-butadiene, cyclopentadiene, 2-methyl prop-2-enoate and ethyl vinyl ether have been theoretically studied using the DFT method at the MPWB1K/cc-pVDZ level of theory. There are two possible modes of participation in each reaction (2π and 4π electron), of which the 2π electron is preferred. The energy results indicate that formations of the [2+4] cycloadducts are favored kinetically. The stereoselectivity of the [2+4] cycloaddition reaction of 2,3-bis (ethylene sulfonyl)-1,3-butadiene with cyclopentane is the highest and the energy barrier for this process is the lowest.

[4 + 2] and [3 + 2] Cycloaddition reactions of 2',3'-dideoxy-3'-nitro-2',3'-didehydrothymidine with ethyl vinyl ether

1993 ◽  
Vol 58 (10) ◽  
pp. 2874-2879 ◽  
Author(s):  
Alexander Papchikhin ◽  
Peter Agback ◽  
Janez Plavec ◽  
Jyoti Chattopadhyaya
Keyword(s):  
Vinyl Ether ◽  
Ethyl Vinyl Ether ◽  
Cycloaddition Reactions ◽  
Ethyl Vinyl
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