O-Arylation versus C-Arylation: Copper-Catalyzed Intramolecular Coupling of Aryl Bromides with 1,3-Dicarbonyls

The copper-catalyzed intramolecular coupling of aryl bromides with 1,3-dicarbonyls via a six-membered ring closure was examined. With CuI (10 mol %) as the catalyst, N,N‘-dimethylethylenediamine as the ligand, and Cs2CO3 as the base, the reactions of α-(2-bromobenzyl)-β-keto esters in THF at refluxing temperature afforded the corresponding substituted 4H-1-benzopyrans in high yields via O-arylation. On the other hand, the reactions of δ-(2-bromophenyl)-β-keto esters in refluxing dioxane led to the formation of 3,4-dihydronaphthalen-2(1H)-one derivatives via C-arylation

Asymmetric Iodolactamization Induced by Chiral Oxazolidine Auxiliary

Asymmetric iodolactamization reactions of unsaturated amides with oxazolidines as the chiral auxiliaries were investigated. With (4S)-4-((2R)-2-butyl)-2,2-dimethyloxazolidine as the auxiliary and LiH as the base, a number of unsaturated amides underwent iodolactamization smoothly to afford the corresponding γ- and δ-lactams in 30−98% yield with de values up to 97%

Facile 5-Endo Amidyl Radical Cyclization Promoted by Vinylic Iodine Substitution

BF3·OEt2-catalyzed atom-transfer radical addition of iodoacetamides to alkynes yielded the corresponding vinyl iodides, which upon treatment with tBuOCl and I2 afforded γ-lactam derivatives in moderate to good yield. The mechanism was proposed to be 5-endo amidyl radical cyclization, and vinylic iodine substitution provided the driving force for the cyclization

Investigation of Bis(tributyltin)-Initiated Free Radical Cyclization Reactions of 4-Pentenyl Iodoacetates

Bis(tributyltin)-initiated atom transfer cyclization reactions of 4-pentenyl iodoacetates (1) at 80 °C led to the formations of 5-(3-iodopropyl)-substituted dihydro-2(3H)-furanones (3) in high yield. With BF3·Et2O as the catalyst, the reactions were run at room temperature to afford the corresponding γ-iodoheptanolactones (2), which could be further transformed into 3-(tetrahydro-2-furyl)propanoic acids (6) upon treatment with aqueous NaHCO3. The reaction mechanism was postulated to be the 8-endo free radical cyclization to generate γ-iodoheptanolactones which easily underwent intramolecular nucleophilic substitution to form bicyclic acylium species (7) as the key intermediate. Subsequent attack by iodide ion furnished γ-lactones while attack by hydroxide ion gave the tetrahydrofuran derivatives

Synthesis of Lactams via Copper-Catalyzed Intramolecular Vinylation of Amides

Copper-catalyzed intramolecular vinylation of iodoenamides were investigated for the first time. With CuI as the catalyst and N,N‘-dimethylethylenediamine as the ligand, a number of iodoenamides underwent cyclization in dioxane leading to the formations of five- to seven-membered lactams in moderate to excellent yields

Self-Protection: The Advantage of Radical Oligomeric Mixtures in Organic Synthesis

Atom-transfer radical oligomers of allyl iodoacetates were converted to 4-pentenoic acids upon treatment with zinc. Reactions of the radical oligomers of various ω-alkenyl iodoacetates with Grignard reagents afforded the corresponding substituted tetrahydrofuran derivatives. These results indicated that radical oligomeric mixtures not only serve as versatile intermediates in organic synthesis, but also exhibit unique advantages in that the oligomeric mixtures are self-protected and the deoligomerization functions as the simultaneous deprotection

Synthesis of Lactams via Copper-Catalyzed Intramolecular Vinylation of Amides

Copper-catalyzed intramolecular vinylation of iodoenamides were investigated for the first time. With CuI as the catalyst and N,N‘-dimethylethylenediamine as the ligand, a number of iodoenamides underwent cyclization in dioxane leading to the formations of five- to seven-membered lactams in moderate to excellent yields

Preference of β-Lactam Formation in Cu(I)-Catalyzed Intramolecular Coupling of Amides with Vinyl Bromides

A general and highly efficient synthesis of 4-alkylidene-2-azetidinones was achieved by the Cu(I)-catalyzed intramolecular C−N coupling of amides with vinyl bromides. This 4-exo ring closure was found to be fundamentally preferred over other modes (5-exo, 6-exo, and 6-endo) of cyclization under copper catalysis. Tandem C−N bond formation was then successfully developed to allow the convenient generation of medium-sized lactams

Activation of the Vinylic C−Cl Bond by Complexation of Fe(CO)₃: Palladium-Catalyzed Coupling Reactions of (η⁴-Chlorodiene)tricarbonyliron Complexes^†

The reactions of 1-chloro- or 2-chloro-substituted (η4-1,3-cyclohexadiene)Fe(CO)3 complexes with terminal alkynes under the catalysis of PdCl2(PPh3)2/CuI at 45−60 °C led to the formation of the corresponding Sonogashira coupling products in 64−97% yields. The complexes also underwent smoothly the intermolecular Heck reactions with activated alkenes under the catalysis of Pd(OAc)2/PPh3 at 60 °C to afford the expected coupling products in 39−83% yields. On the other hand, the corresponding uncomplexed molecule 2-chloro-1,3-cyclohexadiene remained inert under the same reaction conditions. These results clearly demonstrated the strong activation effect of Fe(CO)3 on the oxidative cleavage of the vinylic C−Cl bond

Activation of the Vinylic C−Cl Bond by Complexation of Fe(CO)₃: Palladium-Catalyzed Coupling Reactions of (η⁴-Chlorodiene)tricarbonyliron Complexes^†

The reactions of 1-chloro- or 2-chloro-substituted (η4-1,3-cyclohexadiene)Fe(CO)3 complexes with terminal alkynes under the catalysis of PdCl2(PPh3)2/CuI at 45−60 °C led to the formation of the corresponding Sonogashira coupling products in 64−97% yields. The complexes also underwent smoothly the intermolecular Heck reactions with activated alkenes under the catalysis of Pd(OAc)2/PPh3 at 60 °C to afford the expected coupling products in 39−83% yields. On the other hand, the corresponding uncomplexed molecule 2-chloro-1,3-cyclohexadiene remained inert under the same reaction conditions. These results clearly demonstrated the strong activation effect of Fe(CO)3 on the oxidative cleavage of the vinylic C−Cl bond