Reactions of Nitro Sugars. XXXI. Formation of 2,3- and 3,4-Unsaturated Derivatives in the 6-Deoxyhexose Series

1974 ◽  
Vol 52 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Hans H. Baer ◽  
Chung-Wai Chiu
Keyword(s):  
Methyl Derivative ◽  
Acid Catalyzed ◽  
Threo Isomer

The methyl 3,6-dideoxy-3-nitrohexopyranosides having the α-L-galacto (1), α-L-manno (2), α-L-galacto (3), and α-L-talo (4) configurations and their 2,4-diacetates (6, 11, 16, and 18, respectively) served as starting materials for the preparation of 2,3- and 3,4-unsaturated derivatives. The reactions employed included dehydroacetylation of diacetates and of some monoacetates (5, 7, and 12) that had been obtained by partial acetylation or partial acid-catalyzed de-O-acetylation, and also dehydrations occurring under conditions of acetylation. The following nitroolefins were obtained: methyl 3,4,6-trideoxy-3-nitro-α-L-erythro-hex-3-enopyranoside (8) and its 2-acetate (9), the corresponding α-L-threo isomer (13) and its 2-acetate (10) and 2-O-methyl derivative (20), and methyl 2,3,6-trideoxy-3-nitro-α-L-erythro-hex-2-enopyranoside (14) and its 4-acetate (15) as well as the 4-acetate (17) of the corresponding α-L-threo isomer. In addition, 1,4-di-O-acetyl-2,3,6-trideoxy-3-nitro-α-L-threo-hex-2-enose (19) was obtained by acetolysis of 17. Factors assumed to be responsible for a pronounced regioselectivity in some of the reactions are discussed.

Synthesis, Conformational Analysis and Transannular Reactions of 5,9-Propanobenzo[7]annulene Derivatives

1997 ◽  
Vol 62 (10) ◽  
pp. 1585-1598 ◽  
Author(s):  
Pelayo Camps ◽  
Diana Görbig ◽  
Victoria Muñoz-Torrero ◽  
Francesc Pérez
Keyword(s):  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Related Compound ◽  
Methyl Derivative ◽  
Reaction Conditions ◽  
Molecular Mechanics Calculations ◽  
H Nmr ◽  
Nmr Data ◽  
Acid Catalyzed

(5α,9α,11β)-11-Hydroxy-6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulen-7-one ethylene ketal (6a) and its 11α-methyl derivative (6b) were prepared from monoketal 3. These compounds underwent acid-catalyzed transannular reactions leading to 6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulene derivatives 5a, 8a and 5b, 8b, respectively, depending on the reaction conditions. The compounds 6a and 6b were dehydrated to 6,7,8,9-tetrahydro-5H-5,9-prop[1]enobenzo[7]annulen-7-one (9a) and its 11-methyl derivative (9b), respectively. The conformational analysis of the 5,9-propanobenzo[7]annulene derivatives by molecular mechanics calculations (MM3 program) and the 1H NMR data show that hydroxyketal 6a and the related compound (5α,7β,9α)-6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulen-7-ol (4) exist mainly in the boat-chair conformation with the boat cycloheptenol ring, while for hydroxyketal 6b the chair-boat conformation (chair cycloheptenol ring) seems to be the preferred one.

Synthesis of 8-deoxy-D-erythro-D-galacto-octose. Determination of the configuration of two octenoses

1969 ◽  
Vol 47 (15) ◽  
pp. 2871-2874 ◽  
Author(s):  
D. G. Lance ◽  
W. A. Szarek ◽  
J. K. N. Jones ◽  
G. B. Howarth
Keyword(s):  
Methyl Derivative ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The preparation of 8-deoxy-1,2:3,4-di-O-isopropylidene-D-erythro-α-D-galacto-octopyranose (2) from two octenoses is described. The structure of 2 was established by degradation of its di-O-methyl derivative to 1-deoxy-2,3-di-O-methyl-L-erythritol. This work permits the assignment of configuration to the octenoses. Acid-catalyzed hydrolysis of 2 gave a new higher-carbon sugar, 8-deoxy-D-erythro-D-galacto-octose (4). The synthesis of 1-deoxy-2,3-di-O-methyl-L-threitol and 1-deoxy-2,3-di-O-methyl-D-erythritol is reported.

Acid Catalyzed Furan Ring Transposition

10.1039/sp768 ◽  
2014 ◽  
Author(s):  
Jamsheena V. ◽  
Ravindra Phatake
Keyword(s):  
Furan Ring ◽  
Acid Catalyzed

Catalytic Carbonyl-Olefin Metathesis of Aliphatic Ketones: Iron(III) HomoDimers as Lewis Acidic Superelectrophiles

2018 ◽  
Author(s):  
Haley Albright ◽  
Paul S. Riehl ◽  
Christopher C. McAtee ◽  
Jolene P. Reid ◽  
Jacob R. Ludwig ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Acid Activation ◽  
Lewis Acid Catalysts ◽  
Distinct Mode ◽  
Aliphatic Ketones ◽  
Carbon Carbon Bond ◽  
Metathesis Reactions ◽  
Acid Catalyzed

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

Arylboronic Acid-Catalyzed C-Allylation of Unprotected Oximes

2019 ◽  
Author(s):  
Juha Siitonen ◽  
Padmanabha V. Kattamuri ◽  
Muhammed Yousufuddin ◽  
Laszlo Kurti
Keyword(s):  
Total Synthesis ◽  
Acid Catalysts ◽  
Mechanistic Studies ◽  
Arylboronic Acid ◽  
Synthetic Utility ◽  
Acid Catalyzed

Unprotected keto- and aldoximes are readily <i>C</i>-allylated with allyl diisopropyl boronate in the presence of arylboronic acid catalysts to yield highly-substituted <i>N</i>-alpha-secondary (2°) and tertiary (3°) hydroxylamines. The method’s synthetic utility is demonstrated with the total synthesis of the trace alkaloid <i>N</i>-methyl-euphococcine. Preliminary experimental and computational mechanistic studies point toward the formation of a boroxine as the active allylating species.<br>

Naturally Occurring Organic Acid-catalyzed Facile Diastereoselective Synthesis of Biologically Active (E)-3-(arylimino)indolin-2-one Derivatives in Water at Room Temperature

2019 ◽  
Vol 23 (16) ◽  
pp. 1778-1788 ◽  
Author(s):  
Gurpreet Kaur ◽  
Arvind Singh ◽  
Kiran Bala ◽  
Mamta Devi ◽  
Anjana Kumari ◽  
...  
Keyword(s):  
Room Temperature ◽  
Biologically Active ◽  
Environmentally Benign ◽  
Diastereoselective Synthesis ◽  
Substituted Anilines ◽  
Reaction Conditions ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Reaction Media ◽  
Column Chromatographic

A simple, straightforward and efficient method has been developed for the synthesis of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)- acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone, respectively, using commercially available, environmentally benign and naturally occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium at room temperature. Mild reaction conditions, energy efficiency, good to excellent yields, environmentally benign conditions, easy isolation of products, no need of column chromatographic separation and the reusability of reaction media are some of the significant features of the present protocol.

Ascorbic acid-Catalyzed One-Pot Three-Component Biginelli Reaction: A Practical and Green Approach towards Synthesis of 3,4-dihydropyrimidin- 2(1H)-ones/thiones

2013 ◽  
Vol 10 (7) ◽  
pp. 463-467 ◽  
Author(s):  
Imene Sehout ◽  
Raouf Boulcina ◽  
Boudjemaa Boumoud ◽  
Fabienne Berree ◽  
Bertrand Carboni ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Biginelli Reaction ◽  
One Pot ◽  
Green Approach ◽  
Acid Catalyzed
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