Yi-Long Zhu

Catalytic Dual 1,1-H-Abstraction/Insertion for Domino Spirocyclizations.

A catalytic domino spirocyclization of 1,7-enynes with simple cycloalkanes and cyclo-1,3-dicarbonyls has been established via multiple C-C bond formations from alkynyl/alkenyl functions and dual α,α-C(sp(3))-H abstraction/insertion. The reaction involves addition, 6-exo-dig cyclization and radical coupling sequences under convenient catalytic conditions and provides a concise access to spiro cyclopenta[c]quinolines in good to excellent yields.

Catalytic Arylsulfonyl Radical Triggered 1,7-Enyne Bicyclizations

A new metal-free bicyclization reaction of 1,7-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using tert-butyl hydroperoxide and tetrabutylammonium iodide. The reactions occurred through sulfonylation/6-exo-dig/6-exo-trig bicyclization/in situ desulfonylation/5-exo-trig cyclization/alkyl or alkenyl migration cascade mechanism to give benzo[j]phenanthridines regioselectively.

Metal-Free Iodine-Catalyzed Synthesis of Fully Substituted Pyrazoles and Its Sulphenylation

A direct and metal-free access toward fully substituted pyrazoles and its sulphenylation has been established through an iodine-mediated three-component [3 + 2] annulation of β-ketonitrile (or pentane-2,4-dione), arylhydrazines, and aryl sulfonyl hydrazides. The reaction allows the formation of one C-S and two C-N bonds by the multiple bond cleavage including sulfur-oxygen, sulfur-nitrogen, and carbon-oxygen bonds. The method features low-cost and readily accessible substrates, bond-forming efficiency, and broad substrate scopes as well as simple one-pot operation, which makes this strategy highly attractive.

Metal-Free Radical Haloazidation of Benzene-Tethered 1,7-Enynes Leading to Polyfunctionalized 3,4-Dihydroquinolin-2(1H)-ones

A new cascade three-component haloazidation of benzene-tethered 1,7-enynes for the formation of biologically interesting azidylated 3,4-dihydroquinolin-2(1H)-ones has been achieved under mild and metal-free conditions using TMSN3 as a N3 source and NIS (or NBS or NCS) as a halogen source. The reaction pathway involves in situ-generated azidyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in successive multiple bond-forming events, including carbon-nitrogen, carbon-carbon, and carbon-halogen bonds to rapidly construct complex heterocyclic molecules. Furthermore, the resulting products would be useful building blocks in the discovery of lead compounds and other biologically interesting N3-containing heterocycles.

Metal-free oxidative hydrophosphinylation of 1,7-enynes

A new metal-free oxidative hydrophosphinylation of 1,7-enynes for forming polyfunctionalized 3,4-dihydroquinolin-2(1H)-ones has been realized using readily accessible diarylphosphine oxide and TBPB as an oxidant. The reaction pathway involves an in situ-generated P-centered radical-triggered α,β-conjugate addition/6-exo-dig cyclization/H-abstraction sequence, providing a direct and promising protocol for the formation of C–P, C–C and C–H bonds and rapid construction of complex heterocyclic compounds.

Double SO2 Insertion into 1,7-Diynes Leading to Functionalized Naphtho[1,2-c]thiophene 2,2-dioxides

A novel metal-free double SO2 insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO–bis(sulfur dioxide) under redox-neutral conditions, providing a range of dual sulfone-containing naphtho[1,2-c]thiophene 2,2-dioxides with generally high stereoselectivity. The reaction pathway is proposed to proceed through the sequence of arylsulfonyl-radical-induced 6-exo-dig/5-endo-trig bicyclization, H-abstraction, and diazotization.

Oxidative bicyclization of N-tethered 1,7-enynes toward polycyclic 3,4-dihydroquinolin-2(1H)-ones via site-selective decarboxylative C(sp3)–H functionalization

A new Ag-catalyzed oxidative bicyclization of N-tethered 1,7-enynes with alkylcarboxylic acids for forming 41 examples of polycyclic 3,4-dihydroquinolin-2(1H)-ones has been established using readily accessible K2S2O8 as an oxidant. The reaction pathway involves a silver-catalyzed decarboxylation/in situ-generated C-center radical-triggered α,β-conjugated addition/6-exo-dig cyclization/H-abstraction/5-endo-trig cyclization/SET sequence, allowing direct site-selective decarboxylative C(sp3)–H functionalization toward the formation of multiple C–C bonds and rapid construction of complex spiroheterocycles.

Visible-light-induced methylsulfonylation/bicyclization of C(sp3)-tethered 1,7-enynes using a DMSO/H2O system

A visible light photocatalytic methylsulfonylation/bicyclization of C(sp3)-tethered 1,7-enynes has been established using a dimethyl sulfoxide (DMSO)/H2O system as the methylsulfonyl source. This reaction worked readily to access a wide range of sulfone-containing benzo[a]fluoren-5-ones with one quaternary carbon centre and generally good yields through C–S bond cleavage of DMSO. The reaction mechanism was proposed based on the control experiments.

Pd(II)-Catalyzed Carbonyl-Directing Activation of Alkenes: Selective Fluorosulfonylation and Aminosulfonylation of 1,7-Enynes

A new Pd(II)-catalyzed carbonyl-directing activation of alkenes has been established, enabling radical-induced selective fluorosulfonylation and aminosulfonylation of carbonyl-tethered 1,7-enynes with sulfinic acids and N-fluorobenzenesulfonimide (NFSI) under mild and redox neutral conditions to access densely functionalized ( E)-3,4-dihydronaphthalen-1(2 H)-ones with generally good yields and high stereoselectivity. The selectivity of these bifunctionalizations relies on the electronic nature of substituents on both aryl rings of 1,7-enynes.