[8+3]‐Cycloaddition of Tropones with Azaoxyallyl Cations

Abstract

Althougha zaoxyallyl cations are widely used as 1,3-dipoles for various cycloaddition reactions leading to nitrogen-containing heterocycles, their application in higherorder cycloaddition reaction remains scarce.H erein, we present the [8+ +3]-cycloaddition reaction of tropones with in situ generated azaoxyallyl cations allowing the one-step con-struction of cycloheptatriene-fused 1,4-oxazinones in moderate to good yields. This base-promoted new carbon-oxygen and carbon-nitrogen bond-formingr eaction takes place under mild conditions in the absence of transition metal catalysts.Scheme1.[3+ +x]Cycloaddition reactions of azaoxyallyl cations and [8+ +3] cycloaddition using tropones.[a] Dr.Yellow oil, 0.074 gi n0 .5 mmol scale, 44 %y ield. R f (Pet. ether/ EtOAc = 80/20): 0.57; 1 HNMR (400 MHz, CDCl 3 ): d = 7.36-7.32 (m, 5H), 6.73-6.34 (m, 2H), 6.25-6.11( m, 1H), 5.98 (d, J = 6.7 Hz, 1H),

Diastereoselective [3 + 1] Cyclization Reaction of Oxindolyl Azaoxyallyl Cations with Sulfur Ylides: Assembly of 3,3′-Spiro[β-lactam]-oxindoles

“…In 2011, Jeffrey and coworkers reported the first synthetic application of azaoxyallyl cations in [4 + 3] cycloadditions by using furan or cyclopentadiene, and they also provided experimental evidence to demonstrate the existence of this transient intermediate . Since then, the chemistry of azaoxyallyl cations has been extensively explored by organic chemists, and a variety of [3 + 2] and [3 + 3] cyclizations have been continuously developed during the past decade (Scheme a). Recently, the Chen and Liu group reported an elegant [3 + 1] annulation by using Jeffrey’s azaoxyallyl cations in the presence of sulfur ylides, and a collection of lactams were obtained in moderate to good yields .…”

[8+3]‐Cycloaddition Reactions of Heptafulvenes or Azaheptafulvenes with α‐Halohydroxamates

“…In the past decade, α-halohydroxamate has been established as an ideal and versatile 3-atom reactive species for the synthesis of various bioactive N-containing heterocyclic compounds [10] and natural products. [11] In general, α-halohydroxamates can be converted into azaoxyallyl cations in situ by dehydrohalogenation under basic reaction conditions, followed by reaction with different dipolarophiles for [3 + 1]-, [12] [3 + 2]- [13] [3 + 3]-, [14] [3 + 4]-, [15] and [3 + 8]-cycloadditions, [16] and other reactions. [17] α-Halohydroxamates can also undergo [3 + n]annulation via a tandem addition/intramolecular S N 2 cyclization pathway.…”

Synthesis of spirocyclic oxazole derivatives from 2-arylidene cycloalkanones and α-halohydroxamates

“…In the last decade, the azaoxyallyl cation, which is generated in situ from α-halohydroxamate under basic reaction conditions, has been developed as a new type of versatile 1,3-dipolar compound. 8–11 Recently, azaoxyallyl-cation-involved cycloadditions including [3 + 1], 12 [3 + 2], 13 [3 + 3], 14 [4 + 3] 15 and [8 + 3] 16 cyclization reactions employed to prepare compounds with diverse structures and properties have been developed. In particular, various [3 + 2] cycloaddition reactions of azaoxyallyl cations with carbonyl compounds such as isatins, 13 d cyclic ketones, 13 e cyclopropenones, 13 j vinyl benzoxazinanones, 13 m or thiocarbonyl compounds including cyclopropenethiones and 13 j cyclic thioketones 13 k have been developed to access spirooxazolin-4-one derivatives (Scheme 1).…”