Efficient Metal-Free Synthesis of Heterotriarylmethanes by 1,4-Addition of Benzofuran Azadienes

Abstract

A novel and efficient method has been established for synthesizing a variety of heterotriarylmethanes with good yields by employing a metal-free self-coupling reaction of benzofuran azadienes. The involvement of t-BuONa is essential in this process. Remarkably, this technique boasts mild reaction conditions and exceptional compatibility with various functional groups, rendering it a versatile and invaluable asset in the realm of organic synthesis.

Key words

metal-free synthesis - heterocycles - benzofuran azadienes - heterotriarylmethanes

Publication History

Received: 10 May 2024

Accepted after revision: 22 July 2024

Accepted Manuscript online:
22 July 2024

Article published online:
13 August 2024

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• 14 N,N′-[(Phenylmethylene)bis(1-benzofuran-2,3-diyl)]bis(4-methylbenzenesulfonamide) (2a); Typical Procedure A mixture of 1a (1.0 equiv; 0.2 mmol), t-BuONa (1.0 equiv; 0.2 mmol), and THF (1.0 mL) was kept at 60 °C for 12 h. The mixture was then directly purified by flash column chromatography [silica gel, EtOAc–PE (1:2)] to give a yellow solid; yield: 59.6 mg (90%); mp 95 °C. IR (KBr): 2921, 1451, 1152, 664, 542 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 7.72 (d, J = 8.0 Hz, 4 H), 7.41 (d, J = 8.5 Hz, 2 H), 7.22 (m, 2 H), 7.18 (d, J = 8.0 Hz, 1 H), 7.16–7.11 (m, 7 H), 7.10 (d, J = 6.0 Hz, 1 H), 7.09–7.05 (m, 4 H), 6.69 (d, J = 7.5 Hz, 2 H), 5.68 (s, 1 H), 2.32 (s, 6 H). ¹³C {¹H} NMR (126 MHz, CDCl₃): δ = 153.6, 151.5, 144.1, 136.3, 129.8, 128.2, 127.9, 127.6, 127.2, 126.4, 125.4, 124.9, 123.2, 119.5, 114.7, 111.8, 38.2, 21.5. HRMS (ESI-TOF): m/z [M + H]⁺ calcd for C₃₇H₃₁N₂O₆S₂: 663.1618; found: 663.1623.