Question

The major product formed in the following reaction sequences is: 

• A.
• B.
• C.
• D.

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.

Answer 1

The Correct Option is B

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.

\[ \boxed{\text{Correct product is structure shown in option (B)}} \]