Transition metal-catalyzed synthesis and reactivity of N-alkenyl aziridines

[reaction: see text] Straightforward methods for palladium-catalyzed alkenylation of aziridines with alkenyl halides and copper-catalyzed alkenylation of aziridines with alkenyl boronic acids have been developed. This methodology offers attractive alternatives to the known methods requiring activated alkenyl halides and acetylenes. A wide variety of N-alkenyl aziridines containing substituents other than electron-withdrawing substituents such as cyano groups and sulfones have been synthesized in good yields. Furthermore, these N-alkenyl aziridines exhibit quite a different reactivity from conventional enamines, as demonstrated by their reactivity.     

Manganese-catalyzed cross-coupling reaction between aryl Grignard reagents and alkenyl halides

Aryl Grignard reagents react stereospecifically with alkenyl halides in the presence of manganese chloride (10%) to afford good yields of cross-coupling products.     

Palladium-catalyzed three-component coupling reaction of organic halides, norbornadiene and terminal alkynes

A three-component coupling reaction of organic halides, including aryl halides, methyl iodine, alkenyl iodine and bromoalkynes, with norbornadiene and terminal alkynes catalyzed by a palladium complex and a phase transfer agent in the presence of aqueous NaOH gave 5,6-disubstituted norbornene derivatives in good yields.     

Carbon monoxide free aminocarbonylation of aryl and alkenyl iodides using DMF as an amide source

[reaction: see text] Palladium-catalyzed coupling reaction of N,N-dimethylformamide with aryl or alkenyl halides successfully proceeded in the presence of phosphoryl chloride to afford the corresponding tertiary amides in good yields.     

Novel stereoselective synthesis of 1,3-dienylsilanes via hydromagnesiation reaction of alkynylsilanes

Hydromagnesiation of alkynylsilanes gives (Z)-α-silylvinyl Grignard reagents, which undergo palladium-catalyzed cross-coupling reactions with alkenyl halides to afford stereoselectively 1,3-dienylsilanes in good yields.     

Synthesis of indenes via palladium-catalyzed carboannulation of diethyl 2-(2-(1-alkynyl)phenyl)malonate and organic halides

Highly substituted indenes have been prepared in good yields by the palladium-catalyzed carboannulation of diethyl 2-(2-(1-alkynyl)phenyl)malonate with aryl, benzylic, and alkenyl halides. The reaction conditions and the scope of the process were examined, and a possible mechanism is proposed.     

Enantioselective Synthesis of Isoxazolines Enabled by Palladium-Catalyzed Carboetherification of Alkenyl Oximes

Reported here is a highly efficient Pd/Xiang-Phos catalyzed enantioselective carboetherification of alkenyl oximes with either aryl or alkenyl halides, delivering various chiral 3,5-disubstituted and 3,5,5-trisubstituted isoxazolines in good yields with up to 97 % ee. The sterically bulky and electron-rich (S,Rs)- NMe-X2 ligand is responsible for the excellent reactivities and enantioselectivities. The salient features of this transformation include mild reaction conditions, general substrate scope, good functional-group tolerance, good yields, high enantioselectivities, easy scale-up, and application in the late-stage modification of bioactive compounds. The obtained products can be readily transformed into useful chiral 1,3-aminoalcohols.     

Non-Sonogashira-type palladium-catalyzed coupling reactions of terminal alkynes assisted by silver(I) oxide or tetrabutylammonium fluoride

Palladium-catalyzed reaction of aryl and alkenyl halides with terminal alkynes in the presence of silver(I) oxide as an activator furnishes various arylated or alkenylated alkynes in good to excellent yields. The similar coupling reaction is also found to proceed using tetrabutylammonium fluoride (TBAF) or tetrabutylammonium hydroxide (TBAOH) as an activator.     

Enantioselective Synthesis of Isoxazolines Enabled by Palladium‐Catalyzed Carboetherification of Alkenyl Oximes

Reported here is a highly efficient Pd/Xiang‐Phos catalyzed enantioselective carboetherification of alkenyl oximes with either aryl or alkenyl halides, delivering various chiral 3,5‐disubstituted and 3,5,5‐trisubstituted isoxazolines in good yields with up to 97 % ee. The sterically bulky and electron‐rich (S,Rs)‐ NMe‐X2 ligand is responsible for the excellent reactivities and enantioselectivities. The salient features of this transformation include mild reaction conditions, general substrate scope, good functional‐group tolerance, good yields, high enantioselectivities, easy scale‐up, and application in the late‐stage modification of bioactive compounds. The obtained products can be readily transformed into useful chiral 1,3‐aminoalcohols.     

Copper-catalyzed coupling reactions of alkenyl halides with alkynes in the absence of palladium and ligand

We report herein copper(I)-catalyzed cross-coupling reactions of alkenyl halides with alkynes for the synthesis of 2-alkynyl-buta-1,3-dienes in good to excellent yields. This procedure is the first example for the synthesis of enynes catalyzed by catalytic amount of copper(I) alone in the absence of palladium and any ligand at relatively lower temperature.     

A one‐pot,stereoselective synthesis of 2‐ethoxycarbonyl‐substituted 1,3‐dienes and 1,3‐enynes by hydrostannylation–Stille tandem reaction of tributyltin hydride with alkynyl esters and alkenyl or alkynyl halides

2‐Ethoxycarbonyl‐substituted 1,3‐dienes and 1,3‐enynes can be stereoselectively synthesized in one pot under mild conditions, in good yields, by the palladium‐catalyzed hydrostannylation of alkynyl esters, followed by Stille coupling with alkenyl or alkynyl halides, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Suzuki-Miyaura cross-coupling reactions of potassium alkenyltrifluoroborates

We have previously reported that the palladium-catalyzed cross-coupling reaction of air-stable potassium alkenyltrifluoroborates with aryl halides and triflates proceeds readily with good yields. Recent progress in outlining the scope and limitations of such reactions is described herein. The palladium-catalyzed cross-coupling reaction of potassium alkenyltrifluoroborates with aryl and heteroaryl halides and triflates proceeds readily with moderate to excellent yields. The alkenyl cross-coupling reaction can generally be effected using 2 mol % of PdCl2(dppf).CH2Cl2 as catalyst in i-PrOH-H2O in the presence of t-BuNH2 as the base. A variety of functional groups are tolerated in both partners, and the process is stereospecific with regard to the alkenyltrifluoroborate starting material.     

Organic synthesis with reagents derived from 3R3SiMgMe and MnCl2

Synthetically useful reactions mediated by reagents derived from 3 equiv. of R₃SiMgMe and MnCl₂ are disclosed. (1) The manganese species reacted with terminal acetylenes to give 1,2-disilylated 1-alkenes. Mono- and bis(trimethylsilyl) acetylenes gave tri- and tetrasilylated ethenes, respectively, in good yields. Highly strained tetrakis(trimethylsilyl) ethene has now become easily accessible by this technique. (2) The reaction of alkenyl halides, alkenyl sulfides, and enol phosphates with the title reagents provides vinylsilanes in good yields. The method is also applicable to the synthesis of allylsilanes from allylic sulfides and ethers. (3) Treatment of 1,3-dienes with the manganese reagents provides silylated allylmanganese compounds which add to the carbonyl moiety with high regio-selectivity.     

Nickel‐Catalyzed Cross‐Coupling of Alkyl Zinc Halides for the Formation of C(sp2)?C(sp3) Bonds: Scope and Mechanism

Optimal conditions for a general Ni‐catalysed Negishi cross‐coupling of alkyl zinc halides with aryl, heteroaryl and alkenyl halides have been determined. These conditions allow the reaction to take place smoothly, with low catalyst loading, and in the presence of a wide variety of functional groups to afford products in good yields at room temperature. DFT studies on the mechanism support the occurrence of a catalytic cycle involving transmetalation of the alkyl zinc halide to Ni^I followed by oxidative addition of the haloarene and C? C reductive elimination.     

Synthesis and Some Transformations of 7-Substituted 8-Chlorotheophyllines

Russian Journal of General Chemistry - Alkylation of 8-chlorotheophylline by alkenyl(propargyl) halides yields 7-alkenyl(propargyl)-8-chlorotheophyllines. The reaction of 8-chlorotheophylline with...     

Intramolecular anti-hydrosilylation and silicon-assisted cross-coupling: highly regio- and stereoselective synthesis of trisubstituted homoallylic alcohols

A highly regio- and stereoselective anti-intramolecular hydrosilylation of alkynyl silyl ethers catalyzed by a ruthenium arene complex has been developed. The resultant (Z)-alkylidenesilacyclopentanes are efficiently coupled with aryl or alkenyl halides in the presence of tetrabutylammonium fluoride and a palladium(0) catalyst. The yields are generally good, and the reaction is compatible with a wide range of functional groups. The overall transformation achieves the stereoselective conversion of homopropargyl alcohols to trisubstituted homoallylic alcohols. [reaction: see text]     

Palladium‐catalysed Suzuki cross‐coupling of primary alkylboronic acids with alkenyl halides

The Suzuki reaction of primary alkylboronic acids with alkenyl halides proceeds nicely using the air‐stable catalyst PdCl(C₃H₅)(dppb), Cs₂CO₃ as base and toluene or xylene as solvent. A minor effect of the substituent position of the alkenyl bromide was observed. Quite similar yields were observed in the presence of α‐ or β‐substituted alkenyl bromides such as 2‐bromobut‐1‐ene or 1‐bromo‐2‐methylprop‐1‐ene with this catalyst. This reaction proceeded with a variety of alkylboronic acids such as 2‐phenylethylboronic acid or n‐octylboronic acid. Lower yields of coupling products were obtained in the presence of an alkenyl chloride. Copyright © 2008 John Wiley & Sons, Ltd.     

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)-alkenyl)iodonium tetrafluoroborates with tetrabutyl-ammonium halides: retention of configuration

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)alkenyl)-phenyliodonium tetrafluoroborates 1 with tetrabutylammonium halides (Cl, Br, and I) proceed with exclusive retention of configuration at room temperature and afford (Z)-β-(phenylsulfonyl)vinyl halides 2 in high yields.     

Efficient halogenation of unsaturated organoaluminum compounds with sulfonyl halides

Alkenylalumanes prepared by carbo-or cycloalumination of substituted acetylenes reacted with an equivalent amount of sulfonyl halide (MsCl, TsCl, PhSO₂Cl, MsBr) in methylene chloride or hexane at room temperature to produce alkenyl halides in high yields. Electron-donor solvents such as diethyl ether or tetrahydrofuran inhibited the halogenation process. β-Substituted vinylalumanes generated by hydroalumination of substituted acetylenes failed to react with sulfonyl halides.     

The facile preparation of alkenyl metathesis synthons

We report synthetic methodology allowing the preparation of any length alkenyl halide from inexpensive starting reagents. Standard organic transformations were used to prepare straight chain α-olefin halides in excellent overall yields with no detectable olefin isomerization and full recovery of any unreacted starting material. Reported transformations can be used for the selective incorporation of pure α-olefin metathesis sites in highly functionalized molecules.