Cu(I)-catalyzed synthesis of spiro[isoquinoline-4,2'-[1,3]oxazin]-3-ones via ring expansion reactions of isoxazoles with 4-diazoisoquinolin-3-ones

Modern Dearomative Enlargement of Heteroaromatic Rings

“…Similarly, Lu and Wang recently explored the reactivity of diazo dihydroisoquinolines for the dearomative enlargement of isoxazoles (Scheme 15B). 25 Contrasting with the observations made by Chen and Pu, 24 tetrakis(acetonitrile) copper(I) hexafluorophosphate outperformed both rhodium(II) and palladium(II) catalysts. Moreover, monocyclic isoxazoles were amenable under the developed conditions, thus providing 27 densely functionalized spiro-structures in good yields.…”

Skeletal Editing of (Hetero)Arenes Using Carbenes

“…DFT calculations revealed that the formation of pyrroles and dihydropyrazines was controlled by the 1,5‐ and 1,6‐cyclization of common (5 Z )‐1,4‐diazahexa‐1,3,5‐triene intermediate (Scheme 11c) [63] . Recently, the Lu and Wang group described a copper(I)‐catalyzed ring expansion of isoxazoles into a series of densely substituted spiro[isoquinoline‐4,2′‐[1,3]oxazin]‐3‐ones in good to excellent yield using 4‐diazoisoquinolin‐3‐ones as carbene precursors [64] …”

“…[63] Recently, the Lu and Wang group described a copper(I)-catalyzed ring expansion of isoxazoles into a series of densely substituted spiro[isoquinoline-4,2'- [1,3]oxazin]-3-ones in good to excellent yield using 4-diazoisoquinolin-3-ones as carbene precursors. [64] In 2018, the Liu group reported ligand-controlled [5 + 1] and [5 + 2] annulation of benzo [d]isoxazoles with ynamides for the synthesis of various (Z)-benzo[e] [1,3]oxazine and benzo[f] [1,4]oxazepane derivatives. Whereas the IPrAuCl/AgNTf 2 catalytic system enabled the [5 + 2]-annulation reactions with ynamides, P(t-Bu) 2 (o-biphenyl)AuCl/AgNTf 2 induced the [5 + 1]annulation reactions.…”