RESUMEN
A highly chemo- and regioselective [4 + 2] formal cycloaddition of (Z)-3-iodo allylic nucleophiles and allenamides catalyzed by palladium is reported. The methodology proceeds under mild reaction conditions and is tolerant of alkyl and aryl functional groups. The SN2' substitution at the proximal C[double bond, length as m-dash]C bond performed against the Heck or SN2 pathway delivered a variety of 2-amino-dihydropyrans and 2-amino-tetrahydropiperidines in moderate to satisfactory yields. The [4 + 2] formal cycloaddition derivatives are convertible to interesting scaffolds 2,6,7,7a-tetrahydropyrano[2,3-b]pyrrole and 2,6,7,7a-tetrahydro-1H-pyrrolo[2,3-b]pyridine derivatives via ring-closing metathesis (RCM) with Grubbs catalyst II.
RESUMEN
A novel photocatalytic palladium-induced 6-endo-selective alkyl Heck reaction of unactivated alkyl iodides and alkyl bromides has been described. This strategy facilitates the gentle and efficient synthesis of a variety of 5-phenyl-1,2,3,6-tetrahydropyridine derivatives. It demonstrates a broad substrate tolerance and excellent 6-endo selectivity. Unlike the high-temperature requirements of traditional alkyl Heck reactions, this transformation efficiently proceeds at room temperature and shows significant promise for industrial-scale applications. Mechanistic investigations reveal that this alkyl Heck reaction proceeds via a hybrid palladium-radical process.
RESUMEN
Cyanation of benzylic C-N bonds is useful in the preparation of important α-aryl nitriles. The first general catalytic cyanation of α-(hetero)aryl amines, analogous to the Sandmeyer reaction of anilines, was developed using reductive cyanation with CO2/NH3. A broad array of α-aryl nitriles was obtained in high yields and regioselectivity by C-N cleavage of intermediates as ammonium salts. Good tolerance of functional groups such as ethers, CF3, F, Cl, esters, indoles, and benzothiophenes was achieved. Using 13CO2, a 13C-labeled tryptamine homologue (five steps, 31% yield) and Cysmethynil (six steps, 37% yield) were synthesized. Both electronic and steric effects of ligands influence the reactivity of alkyl nickel species with electrophilic silyl isocyanates and thus determine the reactivity and selectivity of the cyanation reaction. This work contributes to the understanding of the controllable activation of CO2/NH3 and provides the promising potential of the amine cyanation reaction in the synthesis of bio-relevant molecules.
RESUMEN
An efficient method has been developed for the reductive amination of CO2 by using readily available and recyclable oxofluorovanadates as catalysts. Various amines are transformed into the desired N-formylated products in moderate to excellent yields at room temperature in the presence of phenylsilane. Mechanistic studies based on inâ situ infrared spectroscopy suggest a reaction pathway initiated through F-Si interactions. The activated phenylsilane allows for CO2 insertion to produce phenylsilyl formate, which undergoes attack by the amine to generate the target product.
RESUMEN
Correction for 'Pd-Catalyzed oxidative isomerization of propargylic acetates: highly efficient access to α-acetoxyenones via alkenyl Csp2-O bond-forming reductive elimination from PdIV' by Jun Li et al., Chem. Commun., 2016, 52, 10644-10647, DOI: 10.1039/C6CC04463H.
RESUMEN
We report the chiral phosphoric acid catalyzed formal (3 + 2) cycloaddition of 3-substituted 1H-indoles and propargylic alcohols containing a functional directing group (p-NHAc or p-OH). This work represents a straightforward method to synthesize chiral pyrrolo[1,2-a]indole bearing a tetrasubstituted carbon stereocenter. The reaction proceeds smoothly with a wide array of substrate tolerance to deliver various chiral pyrrolo[1,2-a]indoles in up to 93% yield and 98% ee. The utility of this method is highlighted by the diverse transformations of the products into various indole derivatives.
RESUMEN
An efficient one-pot construction of functionalized 3-methylene-5-phenyl-1,2,3,4-tetrahydropyridine derivatives via palladium-catalyzed cyclization-Heck reaction of allenamides has been described. The 3-methylene-5-phenyl-1,2,3,4-tetrahydropyridine derivatives feature a nonconjugated diene, including one endo-enamine and one exocyclic double bond, which could be used for further transformation. Both aryl and vinyl halides performed very well under the standard conditions, delivering the corresponding products efficiently.
RESUMEN
A new type of cascade metallo-ene/Suzuki coupling reaction of allenamides catalyzed by palladium is described. A variety of polyfunctionalized 2,3-dihydropyrrole derivatives, which are important structural motifs for bioactive molecules, were furnished with excellent yields. Two new Csp3-Csp2 bonds were constructed in one pot efficiently. The reductive elimination from π-allyl palladium complex presented excellent regioselectivity to the terminal C1 position. The unique terminal alkene was one of the most easily functionalized groups, providing these molecules with a potential transformation to much more complicated molecules.
RESUMEN
A new type of palladium-catalyzed 6-endo-selective alkyl-Heck reaction of unactivated alkyl iodides has been described. This strategy provides efficient access to a variety of 5-phenyl-1,2,3,6-tetrahydropyridine derivatives, which are important structural motifs for bioactive molecules. This process displays a broad substrate scope with excellent 6-endo selectivity. Mechanistic investigations reveal that this alkyl-Heck reaction performs via a hybrid palladium-radical process.
RESUMEN
A Pd(ii)/(iv)-catalyzed oxidative isomerization of propargylic acetates developed for the synthesis of polysubstituted alkenyl acetates is described. The reductive elimination of alkenyl Csp(2)-OAc bonds from Pd(IV) intermediates is achieved. Mechanistic studies indicate that the reaction mechanism consists of trans acetoxypalladation of a triple bond, isomerization, oxidative addition with PhI(OAc)2 and alkenyl C-OAc bond reductive elimination.