Synthesis of Polysubstituted Naphthalenes by a Hydride Shift Mediated C-H Bond Functionalization/Aromatization Sequence

Quinoline as an Intramolecular Hydride Shuttle in the Deoxygenative Coupling Reaction of Alcohol and the Inert Methyl C(sp3)-H Bond

Reported herein is the C(sp3)-C(sp3) bond-forming at an unactivated C(sp3)-H bond via hydride transfer-initiated deoxygenative coupling reactions. Various polycyclic hydroquinolines were provided under metal-free conditions with excellent diastereoselectivity. Mechanistic study revealed that quinoline served as an intramolecular hydride shuttle to achieve the hydride abstraction and release in order. This methodology not only provides a practical strategy for direct deoxygenative coupling for the C(sp3)-C(sp3) bond-forming but also develops a new reaction type involving quinoline-enabled hydride transfer.

Divergent Aromatization of α-Halobenzyl γ-Butenolides Initiated by Selective Enol Protonation to Benzo[c]fluorenones and Naphthalenes

An unprecedented divergent aromatization reaction of α-halobenzyl γ-butenolides has been described for the selective and concise synthesis of highly substituted benzo and higher π-extended fluorenones, and 1,3-disubstituted naphthalenes depending on the migration ability of the quaternary α-substituent. This aromatization switch from Ag+-mediated planarization to ylidenebutenolides likely originates from selective protonation on the enolic double bond rather than the benzyl halides by TfOH.

Stereoselective synthesis of 6/7/6-fused heterocycles with multiple stereocenters via an internal redox reaction/inverse electron-demand hetero-Diels-Alder reaction sequence

A highly stereoselective synthesis of fused heterocycles with multiple stereocenters via an internal redox reaction/inverse electron-demand hetero-Diels-Alder (IEDHDA) reaction sequence is described. The present reaction sequence has three interesting features: (1) complete control of two potentially competitive processes, i.e., hetero-Diels-Alder reaction and [1,5]-hydride shift; (2) one-shot construction of the complicated 6/7/6-fused heterocyclic structure having multiple stereocenters; and (3) high control of its stereoselectivity. When alkenylidene barbiturates with an allyl benzyl ether moiety were treated with a catalytic amount of Sc(OTf)3 and 2,2'-bipyridine, the internal redox reaction/IEDHDA reaction proceeded successively to afford 6/7/6-fused heterocycles in good chemical yields with good to excellent diastereoselectivities.

Silyl-Group Boosted Internal Redox Reaction: Hydride Shift from an Aliphatic Secondary Position for the Formation of Six- and Seven-Membered Carbocycles

We report a hydride shift/cyclization reaction at the aliphatic secondary position (methylene group). The key to accomplishing this reaction was the employment of benzylidene malonate having a silyl group β to the hydride donor carbon. When the corresponding malonates were treated with a catalytic amount of Al(OTf)3, the [1,5]-hydride shift from the simple aliphatic secondary position proceeded smoothly to afford silyl-group substituted tetralin derivatives in excellent chemical yields (up to 98%). This reaction system was applied to the formation of seven-membered carbocycles via the [1,6]-hydride shift mediated process.