Alkylation reaction of acetonitrile using primary alcohols is effectively catalyzed by [RuHCl(CO)(PPh3)3] in the presence of K3PO4 as a base. Both benzylic and non-benzylic alcohols coupled with acetonitrile to give alkylated nitriles in good yields
Tin-free Giese reactions, employing primary, secondary, and tertiary alkyl iodides as radical precursors, ethyl acrylate as a radical trap, and sodium cyanoborohydride as a radical mediator, were examined in a continuous flow system. With the use of an automated flow microreactor, flow reaction conditions for the Giese reaction were quickly optimized, and it was found that a reaction temperature of 70 °C in combination with a residence time of 10–15 minutes gave good yields of the desired addition products. continuous flow system cyanoborohydride flow chemistry iodoalkanes microreactor tin-free Giese reaction Introduction Organo halides are among the most useful precursors to access
The α-alkylation reaction of acetamides with primary alcohols to afford the corresponding amides was accomplished effectively using RuHCl(CO)(PPh3)3 as a catalyst, nitrogen tridentate ligand L1 as an additive, and KOtBu as a base. While the addition of bpy was effective only for benzylic alcohols, L1 affected the alkylation reaction when both benzylic and non-benzylic type alcohols were used.
A straightforward synthesis of 4,4-spirocyclic indol γ-lactams by tandem radical cyclization of iodoaryl allyl azides with CO was achieved. The reaction of iodoaryl allyl azides, TTMSS and AIBN under CO pressure (80 atm) in THF at 80 °C gave the desired 4,4-spirocyclic indoline, benzofuran, and oxindole γ-lactams in moderate to good yields.
In the absence of transition-metal catalyst, Suzuki-Miyaura coupling reaction between aryl- and alkenylboronic acids and arylpropargylic bromides proceeded to give the corresponding acetylenic products selectively.
Alkyl aryl ketones were synthesized by the carbonylative cross-coupling reaction of alkyl iodides and arylboronic acids under combined Pd/light conditions. In this reaction, it is likely that an acylpalladium species would be formed via carbonylation of the alkyl radical, which would then undergo transmetalation of an arylboronic acid to give the corresponding acyl(aryl)palladium species, ready to undergo reductive elimination to yield the alkyl aryl ketone.
Atom-transfer radical (ATR) reactions of alkenes with R–X usually give products having new C–C and C–X bonds at the adjacent carbons. However, when the reaction was carried out under irradiation using a low-pressure Hg lamp, addition/reduction products were obtained in good yield. Hydrogen bromide, formed by H-abstraction of a bromine radical from alkenes, is likely to play a key role in the reductive ATR reaction.
Carbonylation reactions, such as Heck, Sonogashira, and radical carbonylations, were successfully carried out in a “two-chamber reactor” where carbon monoxide was producedex situ by the Morgan reaction (dehydration of formic acid by sulfuric acid). By a subsequent application in a microflow system using a “tube-in-tube” reactor where gas-permeable Teflon AF2400 was used as the inner tube, it is demonstrated that formic acid/sulfuric acid can be employed concomitantly with an amine base such as triethylamine in the Heck aminocarbonylation of aryl iodide.
Rhodium-catalyzed intramolecular C–H arylation of 2-aryloxybenzoic acids proceeded accompanied by decarbonylation to give dibenzofuran derivatives in high yields. The present reaction is widely applicable to substrates bearing various functionalities.
Tetrabutylammonium decatungstate (TBADT) accelerated the addition of C–H bonds to the N═N double bond of diisopropyl azodicarboxylate (DIAD) under irradiation conditions. The photoinduced three-component coupling between cyclic alkanes, CO, and DIAD was also achieved to give the corresponding acyl hydrazides.
A hydroxymethylation reaction of a variety of iodoarenes proceeded effectively in the presence of CO, NHC-borane, diMeImd-BH3 (2) as a radical mediator, and a catalytic amount of AIBN. The reaction took place chemoselectively at the aryl-iodine bond but not at the aryl-bromine and aryl-chlorine bonds. A three-component coupling reaction comprising aryl iodides, CO, and electron-deficient alkenes also proceeded well to give unsymmetrical ketones in good yields. Control experiments show that 2 would act as a hydrogen donor to acyl radicals and iodinated NHC-borane as a reducing agent of aldehydes.
A free-radical-mediated [2 + 2 + 1] cycloaddition reaction comprising acetylenes, amidines, and CO was achieved by radical chain reaction to give five-membered α,β-unsaturated lactams in good yields. Both acyclic and cyclic amidines reacted with a variety of terminal acetylenes to afford monocyclic, bicyclic, and tricyclic lactams. We propose that vinyl radical carbonylation and nucleophilic addition of the amidine onto the resulting α-ketenyl radical give stable intermediates that are ready to undergo five-membered ring closure with elimination of tin radical.
Bromine radical-mediated cyclopropylcarbinyl-homoallyl rearrangement of alkylidenecyclopropanes was effectively accomplished by C–C bond formation with allylic bromides, which led to the syntheses of 2-bromo-1,6-dienes. A three-component coupling reaction comprising alkylidenecyclopropanes, allylic bromides, and carbon monoxide also proceeded well to give 2-bromo-1,7-dien-5-ones in good yield.