The major product formed in the following reaction sequences is:
Show Hint
In multi-step sequences involving aryl halides and Alpha,Beta-unsaturated esters, Pd-catalyzed Heck coupling followed by hydrogenation and intramolecular cyclization is a common strategy to construct fused heterocycles like indoles.
The reaction proceeds through the following key steps:
Step 1: Heck Coupling
The aryl iodide undergoes a Pd-catalyzed Heck reaction with ethyl 4-bromocrotonate, forming a new C–C bond between the aryl group and the alkene.
Step 2: Reduction and Cyclization
The resulting intermediate contains a double bond and urea functionality. Under H2/Pd-C conditions, the double bond gets reduced. The adjacent nucleophilic nitrogen of the urea attacks the ester-tethered carbon, inducing intramolecular cyclization to form a fused indole-like ring system.
Final Product:
The product is an ethyl ester fused indole compound, as shown in option (B), consistent with the expected mechanism and structure.
\[
\boxed{\text{Correct product is structure shown in option (B)}}
\]
