scholarly journals Regio- and stereoselective ring openings of unsymmetrical oxatricyclo adducts

1997 ◽  
Vol 75 (6) ◽  
pp. 665-680 ◽  
Author(s):  
Simon Woo ◽  
Masood Parvez ◽  
Brian A. Keay
Keyword(s):  
Ring Opening ◽  
High Selectivity ◽  
Alder Reaction ◽  
Diels Alder ◽  
Grignard Reagents ◽  
Electronic Effects ◽  
Diels Alder Reaction ◽  
Ring Opening Reaction ◽  
Organolithium Reagents ◽  
Ring Opening Reactions

SN2′ ring-opening reactions of a number of substituted 11-oxatricyclo[6.2.1.01,6]undec-9-en-5-ones prepared via the intramolecular Diels–Alder reaction employing a furan diene (IMDAF) are reported. Primary, secondary, and tertiary organolithium reagents were capable of effecting the ring-opening reaction, while methyllithium required activation before any ring opening was observed. Hydride reagents, organocuprates, and Grignard reagents were generally ineffective. The ring-opening reaction was highly regio- and stereoselective for attack at C9syn to the bridging oxygen atom provided that C8 was not substituted. A highly stereoselective nucleophilic addition to the carbonyl group anti to the bridging oxygen was also observed. The high selectivity appears to be due to a combination of steric and electronic effects. Keywords: SN2′ reactions, oxatricyclo adducts, Diels–Alder reaction, ring opening.

scholarly journals Towards Thermally Reversible Networks Based on Furan-Functionalization of Jatropha Oil

Molecules ◽  
2020 ◽  
Vol 25 (16) ◽  
pp. 3641
Author(s):  
Frita Yuliati ◽  
Peter J. Deuss ◽  
Hero J. Heeres ◽  
Francesco Picchioni
Keyword(s):  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Epoxide Ring ◽  
Cross Linking ◽  
Jatropha Oil ◽  
Optimum Conditions ◽  
Epoxide Ring Opening ◽  
Diels Alder Reaction ◽  
Ring Opening Reaction

A novel biobased monomer for the preparation of thermally reversible networks based on the Diels-Alder reaction was synthesized from jatropha oil. The oil was epoxidized and subsequently reacted with furfurylamine to attach furan groups via an epoxide ring opening reaction. However, furfurylamine also reacted with the ester groups of the triglycerides via aminolysis, thus resulting in short-chain molecules that ultimately yielded brittle thermally reversible polymers upon cross-linking via a Diels-Alder reaction. A full-factorial experimental design was used in finding the optimum conditions to minimize ester aminolysis and to maximize the epoxide ring opening reaction as well as the number of furans attached to the modified oil. The optimum conditions were determined experimentally and were found to be 80 °C, 24 h, 1:1 molar ratio, with 50 mol % of LiBr with respect to the modified oil, resulting in 35% of ester conversion, 99% of epoxide conversion, and an average of 1.32 furans/triglyceride. Ultimately, further optimization by a statistical approach led to an average of 2.19 furans per triglyceride, which eventually yielded a flexible network upon cross-linking via a Diels-Alder reaction instead of the brittle one obtained when the furan-functionalization reaction was not optimized.

scholarly journals Imidazolinium and amidinium salts as Lewis acid organocatalysts

2012 ◽  
Vol 8 ◽  
pp. 1798-1803 ◽  
Author(s):  
Oksana Sereda ◽  
Nicole Clemens ◽  
Tatjana Heckel ◽  
René Wilhelm
Keyword(s):  
Lewis Acid ◽  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

The application of imidazolinium and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause desulfurization of the products containing a thiol or thiocarbonyl group.

ELECTRONIC EFFECTS AND RATES IN THE DIELS-ALDER REACTION

1952 ◽  
Vol 17 (2) ◽  
pp. 201-206 ◽  
Author(s):  
JOSEPH J. DUDKOWSKI ◽  
ERNEST I. BECKER
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Electronic Effects ◽  
Diels Alder Reaction

Vinylindenes and Some Heteroanalogues in the Diels-Alder Reaction. IX. 3-Vinylbenzofuran and 1,4-Naphthoquinone

1991 ◽  
Vol 44 (7) ◽  
pp. 907 ◽  
Author(s):  
JR Pearson ◽  
QN Porter
Keyword(s):  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

3-Vinylbenzofuran and 1,4-naphthoquinone react to give r-5a,6,c-12a,c-12b-tetrahydroanthra-[1,2-b]benzofuran-5,13-quinone. This adduct undergoes ring opening to 2-(2-hydroxyphenyl)-anthraquinone with base and oxygen, but shows no rearrangement to anthra[2,3-b]benzofuran- 5,13-quinone.

Unusual tandem sequence of oxa Diels–Alder reaction, retro Diels–Alder reaction, and oxa 6π-electrocyclic ring opening in the reaction of 6-amino-4-(4-methoxyphenyl)-2H-pyran-2-ones with benzaldehydes

RSC Advances ◽  
2015 ◽  
Vol 5 (3) ◽  
pp. 2009-2012 ◽  
Author(s):  
Adil I. Khatri ◽  
Shriniwas D. Samant
Keyword(s):  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

The oxa Diels–Alder reaction of 6-amino-4-(4-methoxyphenyl)-2H-pyran-2-ones with benzaldehydes took an unusual path whereby an unexpected tandem sequence of three reactions yielded 3-(4-methoxyphenyl)-5-phenyl-1-(piperidin-1-yl/pyrrolidin-1-yl)penta-2,4-dien-1-ones.

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