Unusual [3+2] Spiroannulation and Creation of Stereogenic Quaternary Center at C‐3 of Oxindole via Addition of (Het)arynes to Isomerized Morita‐Baylis‐Hillman Adduct of Isatin

Abstract

A one‐pot synthesis of 1′‐methyl‐2′‐oxospiro [indene‐1, 3′‐indoline] and 3,3‐disubstituted 2‐oxindole derivatives in excellent combined yield by the reaction of methoxy isomerized MBH adducts of isatin with arynes and heteroarynes has been achieved. A plausible mechanism invoking a [3+2]‐spiro‐ annulation reaction and quenching the intermediate with proton is explained. Formation of regioselective products from unsymmetrical arynes is explained based on reactivity profiles of arynes/heteroarynes. Synthetic utility of synthesized compounds have been demonstrated.

o-Silylaryl Triflates: A Journey of Kobayashi Aryne Precursors

“…It was also found that under elevated temperature (90 °C), a C–C bond insertion reaction occurred, which will be discussed in Scheme b. In a study carried out by Shanmugam et al on the reactivity of isatin-based Morita–Baylis–Hillman (MBH) adducts, they reported a similar C-arylation reaction with arynes, which contained a small amount of [3 + 2] spiroannulation products as well …”

“…In 2017, Srihari, Mehta, and co-workers realized a spiroannulation reaction between substituted N -methyl-3-(carbethoxymethyl)­oxindoles 6-71 and arynes, which could produce the corresponding indano-spirooxindole scaffolds 6-72 in moderate to good yields (Scheme a) . In addition, Shanmugam et al also observed the formation of small amounts of spiroannulation products along with the C-arylation products when isatin based Morita–Baylis–Hillman (MBH) adducts reacted with arynes . In 2016, He and co-workers disclosed that carbazolequinones 6-74 could be obtained in moderate to high yields through a nucleophilic annulation reaction of 2-amino-1,4-naphthoquinones 6-73 with arynes (Scheme b) .…”

“… Among those products, 6,7-bis­[(pinacolato)­boryl]­indole 12-67 could undergo C7-selective Suzuki–Miyaura cross coupling reactions to afford 12-70 . Moreover, Kobayashi precursors of indolynes have been extensively utilized as hetaryne substrates along with benzyne transformations. ,,,,,,,,,,,,,,,, …”

“…In a study carried out by Shanmugam et al on the reactivity of isatin-based Morita−Baylis−Hillman (MBH) adducts, they reported a similar C-arylation reaction with arynes, which contained a small amount of [3 + 2] spiroannulation products as well. 415 Based on a previous observation by Hu and co-workers, the introduction of phenylsulfonyl group on fluorinated carbanions could make them better nucleophiles. Consequently, they realized a nucleophilic fluoroalkylation of arynes with fluorobis(phenylsulfonyl)methane (5-68) furnished fluorobis-(phenylsulfonyl)methylated arenes 5-69 in good to high yields (Scheme 65b).…”

Synthesis of Spiroindenyl-2-Oxindoles through Palladium-Catalyzed Spirocyclization of 2-Bromoarylamides and Vinyl Bromides

“…To achieve this, it is essential to develop efficient synthetic methods for the analysis of compounds of such a type. Currently, the reactions for the synthesis of spiroindenyl-2-oxindoles are rare, and the majority of them rely on the use of 3-substituted indoles as the starting materials (Figure 1a-f) [14][15][16][17][18][19]. It should be noted that Desrosiers and coworkers reported an elegant synthetic approach for spiroindenyl-2-oxindoles through nickel-catalyzed intramolecular Heck cyclization (Figure 1g) [20,21].…”