Propargylic CH activation using a Cu(II) 2-quinoxalinol salen catalyst and tert-butyl hydroperoxide

The oxidation of alkynes to α,β-acetylenic carbonyls was achieved using only 1?mol% of a Cu(II) 2-quinoxalinol salen catalyst with tert-butyl hydroperoxide. These reactions proceed under mild conditions (70?°C) with excellent selectivity, producing yields up to 78%, and were used on a variety of alkyne substrates to produce the desired corresponding α,β-acetylenic ketones. In addition, these reactions can be run under aqueous conditions using a sulfonated version of the 2-quinoxalinol salen with good yields, reducing the need for volatile organic solvents.     

γ-Hydroxy-α,β-acetylenic esters: asymmetric syntheses and applications

γ-Hydroxy-α,β-acetylenic esters are versatile synthetic precursors to many organic compounds. This paper reviews the synthesis of chiral γ-hydroxy-α,β-acetylenic esters by asymmetric reduction of γ-oxo-α,β-acetylenic esters, enantioselective addition to aldehydes in the presence of chiral catalysts, and diastereoselective addition to chiral aldehydes. The preparation of racemic γ-hydroxy-α,β-acetylenic esters is also included. Examples are provided for the application of γ-hydroxy-α,β-acetylenic esters in organic synthesis.     

Stereoselective synthesis of the C(1)-C(12) segment of iriomoteolide 1a: a very potent macrolide antitumor agent

A stereoselective synthesis of the C(1)-C(12) segment of the potent cytotoxic macrolide, iriomoteolide 1a, has been accomplished. The key steps involve an enzymatic kinetic resolution of a β-hydroxy amide, a Pd-catalyzed cross-coupling to a substituted allylsilane, a highly regio- and stereoselective conjugate addition of lithium dimethylcopper to an α, β-acetylenic esters and an elaboration of the C(6)-C(7) trans-olefin geometry by a Julia-Kocienski olefination.     

Synthesis of 2-Acetylenic Carboxylic Acids, 1-Sulfinyl and 1-Sulfonyl-2-ketones from 2-Acetylenic Phenyl Sulfides

Monochlorination at the 1-position with sulfuryl chloride, followed by methanolysis converted 2-acetylenic phenyl sulfides into 1-methoxy-2-acetylenic phenyl sulfides. Oxidation with chromic acid gave 2-acetylenic carboxylic acids.

Oxidation of 2-acetylenic phenyl sulfides with Oxone® and hydrogen peroxide in acetic acid gave the corresponding sulfoxides and sulfones respectively. Diethylamine addition to the triple bond produced enamines which were hydrolyzed with aqueous hydrochloric acid to the corresponding 1-sulfinyl and 1-sulfonyl-2-ketones.     

Zum Mechanismus der α-Alkinon-Cyclisierung: Synthese und Thermolyse von 1-(1-Methylcyclopentyl)[3-13C]prop-2-inon

On the Mechanism of the α-Alkynone Cyclization: Synthesis and Thermolysis of 1-(1-Methylcyclopentyl)[3-¹³C]prop-2-ynone The relative migratory aptitude of two acetylenic substituents in the α-alkynone cyclization, a thermal conversion of α-acetylenic ketones A to 2-cyclopentenones C , was investigated by isotope-labeling experiments. The α-alkynone [β-¹³C]- 1 , specifically labeled with ¹³C at the β-acetylenic C-atom C(3), was synthesized by an intramolecular Witting reaction (230–300°) of the diacylmethylidenephosphorane [¹³C]- 7. The latter resulted from acylation of methylidenetriphenylphosphorane with the acid chloride 4 to yield the acylmethylidenephosphorane 5 , which in turn was formylated with acetic [¹³C]formic anhydride ([¹³C]- 6. ) Upon thermolysis of [β-¹³C]- 1 , its label at C(β) was transferred almost exclusively to C(β) of the 2-cyclopentenone moiety in the resulting cyclization product [¹³C]- 2. We conclude that there is a distinct preference for hydrogen migration in the acetylene → alkylidene carbene isomerization (A → B) which precedes the cyclization step (B → C). No evidence was found for a fast reversibility of this isomerization (A ? B) involving both acetylenic substituents.     

Iron-catalyzed synthesis of polysubstituted pyrroles via [4C+1N] cyclization of 4-acetylenic ketones with primary amines

A highly efficient iron-catalyzed approach to polysubstituted pyrroles has been developed through the [4C+1N] cyclization of 4-acetylenic ketones with primary amines, leading to the synthesis of a variety of tetra- and fully-substituted pyrroles as well as fused pyrrole derivatives in good to excellent yields.     

Conjugate addition of allylic lithium organocuprates and allylic organocopper(I) compounds to α-acetylenic esters

at low temperature, allylic lithium organocuprates and allylic organocopper(I) compounds add stereoselectively (cis-addition) to α-acetylenic esters to afford α,δ-biethylenic esters.     

Reaction of (trimethylstannyl) copper reagents with α, β-acetylenic esters

The stereochemical course of the conjugate addition of various (trimethylstannyl)cuprate (or copper) reagents to α, β-acetylenic esters is dependent on the constitution of the reagent and on the structure of the substrate.     

Synthesis of isoselenazole and its 3- and 5-substituted derivatives

A new method of synthesis for isoselenazole and its 3- and 5-substituted derivatives by one-pot procedure which uses α-acetylenic aldehydes or ketones besides hydroxylamine-O-sulphonic acid and potassium selenide in buffered aqueous solution, is described. When α-acetylenic aldehydes are used, selenobisalkenylnitriles are obtained as side products.     

Aldol reaction of allenolates generated via 1,4-addition of iodide anion or its equivalent to α,β-acetylenic ketones

TMSI, Et₂AlI and (n-Bu)₄NI/TiCl₄ smoothly added to α,β-acetylenic ketones in a 1,4-fashion to yield allenolates $\text{2}$, which reacted with aldehydes providing aldol adducts in good overall yield. A high Z-stereoselectivity was achieved by use of (n-Bu)₄NI/TiCl₄ at −78°C, while a high E-stereoselectivity occurred at 0°C.     

Palladium catalysed tandem cyclisation-anion capture processes.Hydride ion capture by vinylpalladium species.

A new palladium catalysed-anion capture process is proposed, Examples are provided involving cyclisation of o-(ω-acetylenic)-aryl iodides and 2-bromo-1,6-enynes to heterocyclic- and carbocyclic-vinylpalladium species followed by hydride ion capture.     

Nucleophilic Addition-Oxidation Reactions of σ3,λ3 Dialkyl(Silylamino)Phosphines with Mono and Disubstituted Acetylenes

Abstract:

Dialkyl(silylamino)phosphines R₂PNT₂ undergo a nucleophilic addition-oxidation reaction with either mono- or di-substituted acetylenes which is followed by a silyl migration to form phosphoranimines with unsaturated substituents. The reaction route depends on the substituent on the acetylenic carbon atom. Reactions of the acetylenes with dialkyl(silylamino)phosphines show high chemo and regio selectivity for addition to the triple bond in the formation of the alkene phosphoranimines. The reaction of (silylamino)-phosphines with α,β-acetylenic carbonyl compounds is more complicated; the reaction route depends critically on the substituents at both the carbonyl and the β-acetylenic carbon atoms.     

Preparation of Unsaturated Nitriles by the Modification of Mitsunobu-Wilk Procedure II Carbon Elongation of β-Acetylenic Alcohols

An efficient one-step procedure for the converison of β-acetylenic alcohols into the corresponding nitriles using triphenylphosphine (PPh₃)-diethyl azodicarboxylate (DEAD) in the presence of acetone cyanohydrin is described.     

Regio- and stereoselective annelation of phenanthridines with α,β-acetylenic γ-hydroxyacid nitriles

Phenanthridines (3,4-, 7,8-benzoquinolines and methyloctahydrophenanthridine) are annelated regio- and stereoselectively with α,β-acetylenic γ-hydroxyacid nitriles to form new polyfunctional condensed systems, 4-cyanomethylene-1,3-oxazolidino-1,2-dihydrophenanthridines.     

Obtention de δ-methylene δ-lactones et de δ-lactones γ-ethyleniques

Cyclisation in the presence on a catalytic amount of yellow mercury (II) oxide of δ-acetylenic acids and γ-allenic acids leads respectively to δ-methylene-δ-lactones and γ-ethylenic-δ-lactones.     

Three-Component Reaction of Dimethyl Malonate with α,β-Acetylenic Aldehydes and Amines. Synthesis of Push–Pull Buta-1,3-dienes

Russian Journal of Organic Chemistry - Three-component reaction of dimethyl malonate with α,β-acetylenic aldehydes and cyclic secondary amines (pyrrolidine, piperidine, morpholine, and...     

Reaction of 2-aminomethylaziridine with α-unsaturated carbonyl compounds

2-(Substituted vinyl)-1,3-diazabicyclo[3.1.0]hexanes are formed in the reaction of 2-aminomethylaziridine with some -unsaturated carbonyl compounds containing a C=C bond in the a position, whereas 2-(substituted ethynyl)-1,3-diazabicyclo[3.1.0]hexanes are formed with -acetylenic aldehydes. It was established by PMR spectroscopy that the 2-substituted 1,3-diazabicyclo[3.1.0]hexanes are mixtures of endo and exo isomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 758–762, June, 1977.     

Synthesis of α-Acetylenic Aldehydes from 2-Acetylenic Phenyl Sulfides

Monochlorination at the 1 position, with sulfuryl chloride, followed by hydrolysis converted 2- acetylenic phenyl sulfides into 2-acetylenic aldehydes.     

Ruthenium-Catalyzed C−C Coupling of Terminal Alkynes with Primary Alcohols or Aldehydes: α,β-Acetylenic Ketones (Ynones) via Oxidative Alkynylation

The first metal-catalyzed oxidative alkynylations of primary alcohols or aldehydes to form α,β-acetylenic ketones (ynones) are described. Deuterium labelling studies corroborate a novel reaction mechanism in which alkyne hydroruthenation forms a transient vinylruthenium complex that deprotonates the terminal alkyne to form the active alkynylruthenium nucleophile.     

Lewis acid promoted reaction of tetraalkynylstannanes with acyl chlorides: An effective approach towards alkynyl ketones

Tetraalkynylstannanes were found to be atom-economical nucleophilic reagents for the synthesis of α,β-acetylenic ketones. The scope and some limitations of the method are discussed.