Synthesis of Isocoumarins from Cyclic 2-Diazo-1,3-diketones and Benzoic Acids via Rh(III)-Catalyzed C–H Activation and Esterification

Abstract

A mild and efficient Rh(III)-catalyzed C-H activation/esterification reaction for the synthesis of isocoumarins has been developed. This procedure uses readily available benzoic acids and cyclic diazo-1,3-diketones as starting materials and involves domino intermolecular C-H activation in combination with intramolecular esterification to give the corresponding isocoumarins in moderate to excellent yields. This process provides a facile approach for the construction of isocoumarins containing various functional groups that does not require any additives.

Synthesis of Structurally Diversified Benzo[c]chromene Derivatives under (An)aerobic Conditions Catalyzed by CuI

“…Yield: 76% (92 mg); pale yellow solid; mp 127–128°C (lit. mp 125–126°C); 1 H‐NMR (CDCl 3 , 400 MHz): δ H 1.17 (s, 3H), 1.18 (s, 3H), 2.53 (d, J = 3.2 Hz, 2H), 2.80 (d, J = 2.8 Hz, 2H), 7.52–7.56 (m, 1H), 7.78–7.82 (m, 1H), 8.29 (d, J = 7.6 Hz, 1H), 9.05 (dd, J = 8.0 Hz, J ′ = 2.0 Hz, 1H); IR (KBr): ν 3117, 2966, 1736, 1668, 1618, 1482, 1372, 1335, 1323, 1248, 1195, 1155, 1061, 1035, 1022, 780 cm −1 ; HRMS (TOF, ESI, m/z ): Calcd for C 15 H 15 O 3 [M + H] + 243.1016, found 243.1016.…”

“…Yield: 80% (102 mg); pale yellow solid; mp 147–148°C (lit. mp 143–145°C); 1 H‐NMR (CDCl 3 , 400 MHz): δ H 1.18 (s, 6H, 2CH 3 ), 2.51 (s, 3H), 2.52 (s, 2H), 2.79 (s, 2H), 7.35 (dd, J = 8.0 Hz, J ′ = 1.2 Hz, 1H), 8.18 (d, J = 8.0 Hz, 1H), 8.87 (s, 1H); IR (KBr): ν 2965, 2929, 1744, 1675, 1621, 1566, 1488, 1368, 1314, 1249, 1159, 1149, 1033, 904, 830, 776 cm −1 ; HRMS (TOF, ESI, m/z ): Calcd for C 16 H 17 O 3 [M + H] + 257.1172, found 257.1170.…”

“…Yield: 72% (109 mg); pale yellow solid; mp 170–171°C (lit. mp 168–169°C); 1 H‐NMR (CDCl 3 , 400 MHz): δ H 2.53 (s, 3H), 2.85–2.98 (m, 2H), 3.15–3.17 (m, 2H), 3.52–3.59 (m, 1H), 7.29–7.33 (m, 3H), 7.35–7.41 (m, 3H), 8.18 (d, J = 8.0 Hz, 1H), 8.90 (s, 1H); IR (KBr): ν 3163, 3125, 3033, 1717, 1687, 1621, 1598, 1419, 1397, 1299, 1202, 1096, 1048, 1013, 988, 970, 845, 777 cm −1 ; HRMS (TOF, APCI, m/z ): Calcd for C 20 H 17 O 3 [M + H] + 305.1172, found 305.1160.…”

“…Benzo[ c ]coumarin is an important member of this large family whose derivatives also have the widespread applications . In very recent, Yang's group reported that Rh(III)‐catalyzed C─H activation of cyclic 2‐diazo‐1,3‐diketones and benzoic acids was an efficient method, leading to the functional benzo[ c ]coumarins in 2017 (Scheme , (1)). However, the cyclic 2‐diazo‐1,3‐diketone was not a class of available reactants.…”

Selective Carboxylate Directed ortho Functionalization in Copper Catalyzed Reactions of Polyiodo Aromatics: A Straightforward Preparation of 5,7‐Diiodo‐1H‐isochromen‐1‐ones

“…Liu et al reported the possibility of obtaining diversely substituted isocoumarins by using an interesting C–H activation procedure catalyzed by rhodium complexes at 60 °C. More recently, Shang et al reported the rhodium(III)‐catalyzed C–H activation/esterification reaction for the synthesis of isocoumarins that contain a bromine or chlorine atom on the aromatic ring . Finally, Panda et al described the silver‐mediated cyclization of 2‐iodo enol esters to afford 7‐halo 3,4‐disubstituted isocoumarins in moderate to good yields …”