Tandem 1,6-addition/cyclization/vinylcyclopropane rearrangement at low temperature under metal-free conditions: an approach to spiro[4.5]cyclohexadienones

Abstract

A tandem 1,6-addition/cyclization/vinylcyclopropane rearrangement reaction (VCPR) of vinylogous para-quinone methides at low temperature under metal-free conditions has been disclosed for the first time. This method provides an efficient strategy for the construction of a range of spiro[4.5]cyclohexadienones in good yield, exhibiting good functional group tolerance as well as gram-scale capacity.

Time‐Economical Synthesis of Bis‐Spiro Cyclopropanes via Cascade 1,6‐Conjugate Addition/Dearomatization Reaction of para‐Quinone Methides with 3‐Chlorooxindoles

“…An initial deprotonation of 3-chlorooxindoles 2 to form A occurs in the presence of a base. [12] Subsequent nucleophilic attack of carbanion on p-QMs 1 through 1,6-conjugated addition leads to an aromatization intermediate B, [13] which is further transformed into the final product 3 via an intramolecular S N 2-type nucleophilic substitution. [8a,8e,14] Scheme 3.…”

“…1 5, 175.0, 150.1, 149.5, 141.5, 138.7, 137.8, 134.9, 131.2, 127.9, 127.8, 125.9, 125.5, 123.9, 121.6, 110.3, 47.8, 44.4, 43.0, 35.9, 35.6, 29.5, 29.3, 15.4 17 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ = 185. 5, 174.9, 150.1, 149.9, 141.6, 137.7, 134.3, 133.3, 132.1, 132.0, 129.8, 128.0, 127.0, 124.3, 121.7, 110.4, 47.9, 46.1, 43.0, 36.0, 35.6, 29.5, 29.3 Di-tert-butyl-3′-(3-bromophenyl)-dispiro[cyclohexane-1,1′cyclopropane-2′,3′′-indoline]-2,5-diene-2′′,4-dione (3ha).…”

“…1 H NMR (400 MHz, CDCl 3 ) δ = 8.24 (s, 1H), 7.51-7.49 (m, 2H), 7.29 (s, 1H), 7.22 (td, J = 7.6, 2.4 Hz, 2H), 7.03 (d, J = 7.6 Hz, 1H), 6.96 (d, J = 7.6 Hz, 1H), 6.86 (t, J = 7.6 Hz, 1H), 6.63 (d, J = 2.8 Hz, 1H), 6.24 (d, J = 7.6 Hz, 1H), 4.15 (s, 1H), 1.30 (s, 9H), 1.16 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ = 185.4, 174. 5, 150.4, 149.9, 141.5, 137.3, 134.4, 133.9, 133.8, 131.4, 130.2, 130.0, 129.6, 128.1, 125.3, 123.6, 122.4, 121.8, 110.4, 47.4, 43.8, 42.5, 36.0, 35.6, 29.5, 29.3 Di-tert-butyl-3′-(4-bromophenyl)-dispiro[cyclohexane-1,1′cyclopropane-2′,3′′-indoline]-2,5-diene-2′′,4-dione (3ia).…”

“…1 H NMR (400 MHz, CDCl 3 ) δ = 8.61 (s, 1H), 7.51 (d, J = 2.4 Hz, 1H), 7.41 (t, J = 8.4 Hz, 1H), 7.23-7.18 (m, 3H), 7.12 (d, J = 7.6 Hz, 1H), 6.96 (d, J = 7.6 Hz, 1H), 6.86 (t, J = 8.0 Hz, 1H), 6.61 (d, J = 2.4 Hz, 1H), 6.37 (d, J = 7.6 Hz, 1H), 3.99 (s, 1H), 1.99 (s, 3H), 1.29 (s, 9H), 1.13 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ = 185. 4, 174.7, 168.0, 150.1, 150.0, 149.9, 141.3, 137.8, 134.8, 132.2, 129.6, 128.0, 125.6, 125.2, 123.9, 122.7, 121.7, 110.3, 47.4, 43.0, 41.5, 35.8, 35.6, 29.5, 29.1, 20.9.…”

“…1 H NMR (400 MHz, CDCl 3 ) δ = 8.33 (s, 1H), 7.53 (d, J = 2.0 Hz, 1H), 7.36-7.32 (m, 3H), 7.11-7.10 (m, 2H), 6.99 (d, J = 7.6 Hz, 1H), 6.83 (d, J = 7.6 Hz, 1H), 6.67 (d, J = 2.4 Hz, 1H), 6.03 (s, 1H), 4.21 (s, 1H), 2.12 (s, 3H), 1.30 (s, 9H), 1.14 (s, 9H). 13 C NMR (100 MHz, CDCl 3 ) δ = 185. 5, 174.8, 149.7, 149.4, 139.0, 138.0, 135.3, 131.6, 130.9, 130.8, 130.2, 128.3, 128.1, 128.0, 126.5, 124.0, 109.8, 47.8, 44.8, 42.9, 35.9, 35.5, 29.5, 29.2, 21.2 5, 175.7, 149.8, 149.3, 137.9, 135.3, 131.6, 130.8, 130.6, 129.2, 128.6, 128.4, 128.1, 123.5, 123.0, 121.4, 119.6, 48.2, 45.0, 43.0, 35.9, 35.5, 29.5, 29.3, 16 5, 175.8, 149.8, 149.4, 137.9, 135.3, 131.6, 130.8, 130.6, 129.2, 128.5, 128.4, 128.1, 123.5, 123.0, 121.4, 48.2, 45.0, 43.0, 35.9, 35.5, 29.5, 29.3, 16.4 174.8, 150.4, 150.0, 140.5, 137.2, 134.3, 130.9, 130.7, 130.5, 128.6, 128.5, 126.2, 114.2, 111.6, 47.8, 45.1, 43.5, 36.0, 35.6, 29.5, 29. .…”