Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling

Abstract

The oxidative treatment of (m)ethyl 2‐aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C–C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems.

Design, Synthesis and Anticancer Evaluation of Spiro [cyclohexane‐1,1′‐indene]‐2,5‐diene Analogues

“…The structure of Spiro‐ester 4 was further re‐confirmed by 2D 1 HNMR experiments viz., HSQC and HMBC (refer SI). The plausible mechanism for the conversion of open chain ester 3 to Spiro‐ester 4 is depicted in Scheme . Hydrolysis of Spiro‐ester 4 using 2 N NaOH in methanol at 65 °C for 18 h gave key intermediate Spiro‐acid 5 in 80% yield ( Scheme ).…”

MoV Reagents in Organic Synthesis

“…Depending on the substitution pattern of the starting materials 23 , spirocyclic compounds are accessible through MoCl 5 ‐mediated oxidative coupling reactions (Scheme ) 62. Activation of the tertiary carbon atom (labelled "t" in Scheme ) gives the corresponding phenanthrene derivative 24 , whereas activation of the quaternary carbon atom (labelled "q") leads to the formation of the corresponding spiro compound 51 (Scheme and Scheme , a).…”

“… Depending on the substitution pattern of the starting material 23 , either the corresponding phenanthrene derivative 24 or the corresponding spiro compound 51 is formed 62…”

“… Synthesis of (a) five‐, or (b) six‐membered spirocyclic molecules through oxidative coupling with MoCl 5 /TiCl 4 62…”

“… Postulated mechanistic course for the generation of spirocyclic compounds from 2‐aryl‐substituted cinnamates 62…”