Platinum‐Catalyzed Cyclization/[1,2]‐Alkyl Migration/Allyl Shift/Cyclization Cascade of Epoxy Alkynyl Allyl Ethers: A Step‐Economical Route to Spirobenzo[h]chromanones

Abstract

In tandem: A PtI4‐catalyzed tandem reaction of epoxy alkynyl allyl ethers involving a cyclization, [1,2]‐alkyl migration, O→C allyl shift, aromatic cyclization sequence has been achieved to synthesize spirobenzo[h]chromanones. The reaction simultaneously forms two adjacent stereocenters, one of which is a quaternary carbon atom (see scheme).

Gold-Catalyzed 1,1-Carboalkoxylation of Oxetane-Ynamides via Exocyclic Metal Carbenes: Divergent and Atom-Economical Synthesis of Tricyclic N-Heterocycles

“…This can be explained by the fact that the generated carbocation after hydride shift can be stabilized by an alkyl group (R = alkyl). In the cases where chiral ynamides are employed, the reaction would undergo stereospecific ring expansion through path b via a transition state TS B to produce the corresponding chiral intermediates C and eventually the chiral tricyclic N-heterocycle products.…”

When Alkyne π-Activation Meets Pinacol-Type [1,2]-Rearrangement: On the Invention of Domino Reactions for the Synthesis of Carbocycles and Heterocycles

“…Notably, when the starting material contained an allyl ether group instead of a free hydroxy group, the corresponding spirobenzo[h]chromanones were formed through an additional allyl shift. 58 Scheme 24 Synthesis of spiropyranones by the method of Liang and co-workers…”

Cu(TFA)2-Catalyzed Oxidative Tandem Cyclization/1,2-Alkyl Migration of Enamino Amides for Synthesis of Pyrrolin-4-ones

“…Classic 1,2-alkyl migration reactions, such as pinacol rearrangement and α-ketol rearrangement, are well established in organic synthesis . Recently, transition-metal catalyzed tandem reactions along with 1,2-alkyl migration have been found to be a powerful strategy for the rapid construction of complex molecules . Our interest in the cyclization of enamines or enamides for the synthesis of azaheterocycles prompted us to study the oxidative cyclization of enamines.…”