A highly stereoselective preparation of syn-1,2-diols from secondary α-allenic alcohols via iodocyclization. Synthesis of (±)-threo-L-factor and (±)-disparlure

1994 ◽  
Vol 72 (8) ◽  
pp. 1857-1865 ◽  
Author(s):  
Richard W. Friesen ◽  
André Giroux
Keyword(s):  
Nitrogen Atom ◽  
Cyclization Reaction ◽  
Reaction Sequence ◽  
Terminal Olefin ◽  
Isomeric Mixture ◽  
Silver Carbonate ◽  
Synthetic Utility ◽  
Vinyl Iodide ◽  
Hydrolysis Of ◽  
Initial Process

The iodocyclization of the N-tosyl carbamates 5 of secondary α-allenic alcohols 4 is described. The reaction sequence involves the addition of iodine to the terminal olefin of the allene moiety of 5 resulting in the formation of an isomeric mixture of Z and E diiodides 6 and 7. This initial process is followed, in the same pot, by reaction of the diiodides with silver carbonate. Hydrolysis of the resulting trans imino carbonates 8 provides syn-1,2-diols 10 in a highly diastereoselective (>50:1) and regioselective (>20:1) fashion. Oxazolidinones 9 are minor products that arise from the participation of the carbamate nitrogen atom in the cyclization reaction. The regioselectivity of the cyclization reaction from 6/7 to 8 is highly dependent upon the reaction solvent with the optimum results being obtained in ether/MeCN mixtures (10:1 to 50:1) or CH2Cl2. The synthetic utility of the vinyl iodo diols 10 is demonstrated by the synthesis of (±)-threo-5-hydroxy-4-decanolide (17) ((±)-threo-L-factor) and (±)-cis-7, 8-epoxy-2-methyloctadecane (24) ((±)-disparlure). The key step in each synthesis involves the conversion of the vinyl iodide moiety of 10 into the alkynes 15 or 18 (from 10j and 10k, respectively) via a high-yielding dehydrohalogenation reaction.

Thioamide dianions derived from N-arylmethyl thioamides: Generation and application as carbon nucleophiles adjacent to the nitrogen atom

2010 ◽  
Vol 82 (3) ◽  
pp. 541-554 ◽  
Author(s):  
Toshiaki Murai
Keyword(s):  
Nitrogen Atom ◽  
Electronic Properties ◽  
Cyclization Reaction ◽  
Carbon Nucleophiles ◽  
Ready Availability

This review illustrates the ready availability of thioamide dianions and their versatility as carbon nucleophiles adjacent to the nitrogen atom. The products derived from the addition of thioamide dianions to a range of electrophiles can participate in a cyclization reaction to form nitrogen-containing heterocycles. The electronic properties of thioamide dianions are also considered.

scholarly journals Unexpected Resistance to Base-Catalyzed Hydrolysis of Nitrogen Pyramidal Amides Based on the 7-Azabicyclic[2.2.1]heptane Scaffold

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2363 ◽  
Author(s):  
Diego Ocampo Gutiérrez de Velasco ◽  
Aoze Su ◽  
Luhan Zhai ◽  
Satowa Kinoshita ◽  
Yuko Otani ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Amide Bond ◽  
Free Energies ◽  
Amide Nitrogen ◽  
Bond Rotation ◽  
Entropy Term ◽  
And Inversion ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Amide Nitrogen Atom

Non-planar amides are usually transitional structures, that are involved in amide bond rotation and inversion of the nitrogen atom, but some ground-minimum non-planar amides have been reported. Non-planar amides are generally sensitive to water or other nucleophiles, so that the amide bond is readily cleaved. In this article, we examine the reactivity profile of the base-catalyzed hydrolysis of 7-azabicyclo[2.2.1]heptane amides, which show pyramidalization of the amide nitrogen atom, and we compare the kinetics of the base-catalyzed hydrolysis of the benzamides of 7-azabicyclo[2.2.1]heptane and related monocyclic compounds. Unexpectedly, non-planar amides based on the 7-azabicyclo[2.2.1]heptane scaffold were found to be resistant to base-catalyzed hydrolysis. The calculated Gibbs free energies were consistent with this experimental finding. The contribution of thermal corrections (entropy term, –TΔS‡) was large; the entropy term (ΔS‡) took a large negative value, indicating significant order in the transition structure, which includes solvating water molecules.

A Tandem C-Acylation-Cyclization Reaction Sequence for the Synthesis of New N-Acyl-3-substituted 1,8-Naphthyridine-2,4-diones

Heterocycles ◽  
1999 ◽  
Vol 51 (7) ◽  
pp. 1609 ◽  
Author(s):  
Olga Igglessi-Markopoulou ◽  
Alexandros Zografos ◽  
Christos Mitsos
Keyword(s):  
Cyclization Reaction ◽  
Reaction Sequence

Photocatalytic xanthate-based radical addition/cyclization reaction sequence toward 2-biphenyl isocyanides: synthesis of 6-alkylated phenanthridines

2020 ◽  
Vol 18 (18) ◽  
pp. 3487-3491 ◽  
Author(s):  
Pedro López-Mendoza ◽  
Luis D. Miranda
Keyword(s):  
Radical Addition ◽  
Cyclization Reaction ◽  
Modular Approach ◽  
Reaction Sequence

A photocatalytic xanthate-based radical addition/cyclization reaction cascade toward 2-biphenylisocyanides is described as a practical and modular approach to 6-alkylated phenanthridines.

Synthesis of 3-(4′-Methoxyphenyl)-2,2,4,4-Tetramethylpentane and Some Cyclic Analogs

1986 ◽  
Vol 39 (12) ◽  
pp. 2095 ◽  
Author(s):  
DJ Collins ◽  
HA Jacobs
Keyword(s):  
Methanesulfonic Acid ◽  
Similar Reaction ◽  
Reaction Sequence ◽  
Quinone Methides ◽  
Hydride Reduction ◽  
Lithium Aluminium ◽  
Clemmensen Reduction ◽  
Analogous Manner ◽  
Hydrolysis Of ◽  
Zinc Iodide

Reaction of 1-methoxy-2-methyl-1-trimethylsilyloxyprop-1-ene (8) with 1-acetoxy-1-(4′-methoxyphenyl)-2,2-dimethylpropane (7b) in the presence of zinc iodide gave 84% of methyl 3-(4′methoxyphenyl)-2,2,4,4- tetramethylpentanoate (9a), which was reduced with lithium aluminium hydride to 3-(4′-methoxyphenyl)-2,2,4,4-tetramethylpentan-1-ol(12a). Hydride reduction of the derived tosylate (12b) afforded 3-(4′-methoxyphenyl )-2,2,4,4-tetramethylpentane (5b) which upon demethylation yielded the corresponding phenol (10a). In an analogous manner, 1-acetoxy-1-(4′-methoxyphenyl)-2-methylpropane (7d) was converted into 3- (4′-hydroxyphenyl)-2,2,4-trimethylpentane (10b). By a similar reaction sequence, 6-methoxy-2,2-dimethyl-3,4- dihydronaphthalen-1(2H)-one (14) was transformed into 6-hydroxy-2,2- dimethyl-1-(1′,1′-dimethylethyl)-1,2,3,4-tetrahydronaphthalene (16b). Hydrolysis of the ester (9a) and cyclization of the resulting carboxylic acid (19) by treatment with methanesulfonic acid at 20° for 18 h afforded 3-(1′, 1′-dimethylethyl)-6-methoxy-2,2-dimethyl-2,3-dihydro-1H-inden-1-one (20). Clemmensen reduction of this followed by demethylation yielded 1-(1′,1′-dimethylethyl)-2,2-dimethyl-2,3-dihydro-1H-inden-5-ol (21b). Attempts to oxidize the phenols (10a), (10b), (16b) and (21b) to the corresponding quinone methides by conventional methods failed.

Micellar Catalysis of Organic Reactions. XVII. Hydrolysis of Nitrazepam and Some N-Alkylated Derivatives

1985 ◽  
Vol 38 (7) ◽  
pp. 1037 ◽  
Author(s):  
TJ Broxton ◽  
SR Morrison
Keyword(s):  
Aqueous Solution ◽  
Nitrogen Atom ◽  
Sodium Dodecyl Sulfate ◽  
Sodium Dodecyl ◽  
Initial Attack ◽  
Amide Nitrogen ◽  
High Acid ◽  
Alkyl Derivatives ◽  
Hydrolysis Of ◽  
Amide Nitrogen Atom

Product studies for the acid catalysed hydrolysis of nitrazepam and some N-alkyl derivatives in the presence of micelles of sodium dodecyl sulfate ( sds ) have been carried out by a U.V. spectrophotometric technique. Attack of water at C2 leading to initial amide cleavage is favoured by high acid concentrations, by micelles of sds and by small R groups attached to the amide nitrogen atom. For nitrazepam, a change of mechanism from water attack at C5 (leading to initial azomethine cleavage) to water attack at C2 (leading to initial amide cleavage) was observed on transfer from water to micelles of sds . For N-benzyl nitrazepam (1d), however, no change of mechanism was detected. Initial attack of water occurred at C5 (leading to initial azomethine cleavage), both in aqueous solution and in micelles of sds.

scholarly journals Synthesis of a new class of aminocyclitol analogues with the conduramine D-2 configuration

2010 ◽  
Vol 6 ◽  
Author(s):  
Latif Kelebekli ◽  
Yunus Kara ◽  
Murat Celik
Keyword(s):  
Double Bond ◽  
Cyclization Reaction ◽  
Spectroscopic Methods ◽  
New Class ◽  
Hydrolysis Of

A new class of aminocyclitol derivatives with the bicyclo[4.2.0]octane skeleton was synthesized starting from cyclooctatetraene. Photooxygenation of trans-7,8-diacetoxy- and cis-7,8-dichlorobicyclo[4.2.0]octa-2,4-diene afforded the bicyclic endoperoxides. Reduction of the latter with thiourea followed by a Pd(0) catalyzed ionization/cyclization reaction gave the corresponding oxazolidinone derivatives. Oxidation of the double bond with KMnO4 or OsO4 followed by acetylation gave the acetate derivatives, the exact configuration of which was determined by spectroscopic methods. Hydrolysis of the oxazolidinone rings and removal of the acetate groups furnished the desired aminocyclitols.

Mechanism of formation of trimethylisoxazole and intermediates upon alkaline hydrolysis of nitroethane

1969 ◽  
Vol 47 (17) ◽  
pp. 3107-3112 ◽  
Author(s):  
R. W. Lockhart ◽  
K. W. Ng ◽  
P. E. Nott ◽  
A. M. Unrau
Keyword(s):  
Alkaline Hydrolysis ◽  
Initial Step ◽  
Mechanism Of Formation ◽  
Reaction Sequence ◽  
Simple Mechanism ◽  
Basic Hydrolysis ◽  
Elimination Reactions ◽  
Hydrolysis Of

Nitroethane and higher homologous primary nitroalkanes undergo a base-catalyzed condensation yielding the corresponding 2,3,4-trialkyisoxazoles. Basic hydrolysis of nitroethane to acetaldehyde is the key initial step followed by a series of condensation and elimination reactions. Through the use of appropriately 14C-labelled intermediates and acetaldehyde-d4, a relatively simple mechanism is indicated which will satisfactorily account for all observed intermediates indicated in a summary of the reaction sequence.[Formula: see text]

scholarly journals Ketyl radical reactivity via atom transfer catalysis

Science ◽  
2018 ◽  
Vol 362 (6411) ◽  
pp. 225-229 ◽  
Author(s):  
Lu Wang ◽  
Jeremy M. Lear ◽  
Sean M. Rafferty ◽  
Stacy C. Fosu ◽  
David A. Nagib
Keyword(s):  
Functional Group ◽  
Atom Transfer ◽  
Ketyl Radical ◽  
Radical Reactivity ◽  
Atom Transfer Radical Addition ◽  
Synthetic Utility ◽  
Vinyl Iodide ◽  
Dimanganese Decacarbonyl ◽  
Electron Reduction

Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals. The in situ conversion of aldehydes to α-acetoxy iodides lowers their reduction potential by more than 1 volt, allowing for milder access to the corresponding ketyl radicals and an oxidative termination event. Upon subjecting these iodides to a dimanganese decacarbonyl precatalyst and visible light irradiation, an atom transfer radical addition (ATRA) mechanism affords a broad scope of vinyl iodide products with highZ-selectivity.

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