ABSTRACT
A highly diastereoselective dearomatization of indoles via palladium-catalyzed decarboxylative alkynyl termination was developed. This protocol provides dissimilar tetracyclic and tetrasubstituted indoline scaffolds bearing congested stereocenters, which led to operationally simple conditions, short time, and broad substrate scope. Additionally, this reaction system could be scaled to gram quantities in a satisfactory yield and diastereoselectivity.
ABSTRACT
We have developed a highly selective method for the synthesis of α,ß-unsaturated amides and alkenyl nitriles from readily available propargylic alcohols. The reaction proceeded smoothly under the neutral conditions with hydroxylamine hydrochloride (NH2OH·HCl) as the nitrogen source. The development of these new strategies has significantly extended the application of hydroxylamine hydrochloride to the chemistry of propargylic alcohols. Moreover, both secondary and tertiary alcohols have been highly regioselectively transformed to the desired products with good functional group compatibility.
ABSTRACT
The first palladium-catalyzed ring opening of norbornene to prepare methylenecyclopentane derivatives has been established. The process, which uses readily available aryl iodides, tosylhydrazones and norbornene as starting materials, likely takes place via tandem Heck-type coupling, palladium carbene migratory insertion, C-C bond cleavage and the ß-hydride elimination pathway in a single synthetic sequence.
ABSTRACT
A novel and convenient metal-free nitration and cyclization of 1,6-enynes has been developed. Two C-C bonds and one C-N bond were constructed in one process in this reaction. This transformation is proven to have relatively good functional-group applicability and can be scaled up to gram quantities in satisfactory yields. According to the following experimental facts and related literature reports, a radical pathway was involved in this transformation.
Subject(s)
Alkenes/chemistry , Alkynes/chemistry , Cyclic N-Oxides/chemistry , Nitrites/chemistry , CyclizationABSTRACT
A novel BF3·Et2O-promoted tandem reaction of easily prepared 2-propynolphenols/anilines and trimethylsilyl azide is developed to give C2-alkenylated benzoxazoles and benzimidazoles in moderate to good yields. Most reactions could be accomplished in 30 min at room temperature. This tandem process involves a Csp-Csp2 bond cleavage and a C-N bond formation. Moreover, both tertiary and secondary propargylic alcohols with diverse functional groups were tolerated under the mild conditions.
Subject(s)
Aniline Compounds/chemistry , Benzimidazoles/chemical synthesis , Benzoxazoles/chemical synthesis , Boranes/chemistry , Phenols/chemistry , Benzimidazoles/chemistry , Benzoxazoles/chemistry , Molecular StructureABSTRACT
A novel iron-catalyzed aerobic oxidative reaction to synthesize disubstituted isoxazoles from homopropargylic alcohol, t-BuONO, and H2O is developed. The method provides mild conditions to afford a variety of useful substituted heterocycles in an efficient and regioselective manner. The mechanism has been studied and proposed, which indicates that the transformation can be realized through construction of a CâN bond and CâO bond, C-H oxidation, and then cyclization. Moreover, this method can be enlarged to gram scale.
Subject(s)
Isoxazoles/chemical synthesis , Catalysis , Cyclization , Hydrogen Bonding , Iron/chemistry , Isoxazoles/chemistry , Molecular Structure , Oxidation-ReductionABSTRACT
A new method with high efficiency for the synthesis of α,ß-unsaturated amides from the easily prepared propargyl alcohols and TMSN3 using TMSCl as an acid promoter is developed. A wide variety of α,ß-unsaturated amides were produced in moderate to excellent yields. Mechanistic studies indicate that this transformation involves TMSCl-mediated allenylazide intermediate formation, C-C bond cleavage, and C-N bond formation. Significantly, this reaction shows good functional group compatibility and high regioselectivity, with a relatively short reaction time and inexpensive reagents.
ABSTRACT
A novel copper-catalyzed one-pot functionalization of homopropargylic alcohols that involves trifluoromethylation, aryl migration, and formation of a carbonyl moiety has been developed. This reaction constitutes the first direct conversion of homopropargylic alcohols into CF3-containing 3-butenal or 3-buten-1-one derivatives in a regioselective manner. Mechanistic studies indicate that the 1,4-aryl migration proceeds through a radical pathway.