Ke-Gong Ji

Selective Functionalization of sp3 C−H Bonds Adjacent to Nitrogen Using (Diacetoxyiodo)benzene (DIB)

A PhI(OAc)(2) mediated selective functionalization of sp(3) C-H bonds adjacent to a nitrogen atom has been reported. When piperidine derivates were used, direct diacetoxylation of alpha and beta sp(3) C-H adjacent to a nitrogen atom were observed to afford various cis-2,3-diacetoxylated piperidines. On the other hand, tetrahydroisoquinoline derivatives gave various alpha-C-H functionalized products in the presence of PhI(OAc)(2). Nitroalkanes, dialkyl malonates, and beta-keto ester are active participants in this coupling reaction. Meanwhile, alpha-amino nitriles can also be obtained by oxidative coupling of amines with malononitrile.

Synthesis of Isoquinoline Derivatives via Ag-Catalyzed Cyclization of 2-Alkynyl Benzyl Azides

Ag-catalyzed cyclization of 2-alkynyl benzyl azides offers a novel and efficient method for the synthesis of substituted isoquinoline. The reaction proceeds smoothly in moderate to good yields and tolerates considerable functional groups. The reaction conditions and the scope of the process are examined, and a plausible mechanism is proposed.

Electrophile-driven regioselective synthesis of functionalized quinolines.

Highly substituted 3-iodoquinolines bearing different alkyl and aryl moieties can be synthesized in moderate to excellent yields (up to 99%) by 6-endo-dig iodocyclization of 2-tosylaminophenylprop-1-yn-3-ols with molecular iodine (I(2)) under mild conditions. The cyclization is highly regioselective and the resulting 3-iodoquinolines can be further functionalized by various coupling reactions.

Platinum-catalyzed cross-dehydrogenative coupling reaction in the absence of oxidant

A third strategy for cross-dehydrogenative coupling reaction has been reported via platinum-catalyzed sp(3) C-H and sp(3) C-H coupling reaction in the absence of oxidant. Nitroalkanes as well as dialkyl malonate derivatives, beta-keto esters and malononitrile are active participants in this coupling reaction. Both cyclic and acyclic non-activated simple ketones are good reactants in this reaction.

Platinum-Catalyzed Michael Addition and Cyclization of Tertiary Amines with Nitroolefins by Dehydrogenation of α,β-sp3 C−H Bonds

A mild platinum-catalyzed oxidative dehydrogenation of alpha,beta-C(sp(3))-H bonds of tertiary amines in the presence of ambient oxygen is revealed, and the in situ formed enamines subsequently reacting with various nitroolefins resulted in the development of two one-pot synthetic protocols involving Michael addition-elimination and Michael addition-cyclization. By using different functionalized nitroolefins compatible with the current oxidative conditions, two types of structurally divergent products, trisubstituted enamines and chromano[2,3-b]piperidines, could be expediently accessed, respectively.

Au-catalyzed tandem cyclization/[1,2]-alkyl migration reaction of epoxy alkynes: synthesis of spiropyranones.

A novel gold-catalyzed tandem cyclization/[1,2]-alkyl migration process of epoxy alkynes to spiropyranones has been discovered. From this process, the construction of adjacent multiple stereocenters with a new quaternary carbon atom is achieved. The gold-catalyzed domino process is stereospecific with respect to the migrating carbon atom. A type of unusual C-C bond cleavage of epoxide systems has also been discovered, which can lead to the formation of two Z alkenes and a carbonyl functional group in one step with excellent stereoselectivity. Furthermore, this efficient domino process could be achieved in the presence of the simplest and least expensive gold catalyst [NaAuCl(4)].2H(2)O with a low catalyst loading.

Synthesis of five- and six-membered dihalogenated heterocyclic compounds by electrophile-triggered cyclization

Highly substituted dihalogenated dihydrofurans, dihydropyrroles, and dihydro-2H-pyrans bearing alkyl, vinyl, aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I(2), IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling reactions. The presence of trace amount of water is essential for this electrophilic cyclization.

Electrophilic Carbocyclization of Aryl Propargylic Alcohols: A Facile Synthesis of Diiodinated Carbocycles and Heterocycles

Diiodinated carbocycles and oxygen heterocycles can be readily synthesized by electrophilic carbocyclization of aryl propargylic alcohols in moderate to good yields under mild conditions. The resulting diiodide can be further exploited by subsequent oxidizing and coupling reactions. Both the iodine anion and cation generated from I(2) are used effectively. The presence of a trace amount of water is essential for this electrophilic cyclization.

PtCl2-catalyzed tandem triple migration reaction toward (Z)-1,5-dien-2-yl esters.

A novel method for the selective synthesis of (Z)-1,5-dien-2-yl esters has been developed though Pt(II)-catalyzed tandem 1,2-acyl and 1,2-hydride migration, along with an allyl migration reaction of propargylic carboxylates with electronically unbiased internal alkynes. The unusual selectivity of 1,2-acyloxy migration was realized.

Platinum-Catalyzed Cycloisomerization Reaction of 1,6-Enyne Coupling with Rearrangement of Propargylic Esters

A platinum-catalyzed cycloisomerization of 1,6-enyne coupling with the rearrangement chemistry of propargylic ester has been developed. Most probably, under platinum catalysis, propargylic ester undergoes the 1,3-acyloxy migration to afford metal allene intermediate, which is followed by the Diels-Alder-type reaction. 1,3-Acyloxy migration is the key step during the transformation.