The major product formed in the following reaction is

CSA = camphorsulfonic acid

Concept:

• [3,3] sigmatropic reaction is a class of pericyclic reactions whose stereochemical outcome is governed by the geometric requirements of the cyclic transition state.
• These reactions generally proceed via a chair-like transition state where 1,3-diaxial interactions are minimized.
• The Mannich reaction is a three-component organic reaction that involves the amino alkylation of an acidic proton subsequent to a carbonyl functional group by formaldehyde and a primary or secondary amine or ammonia. The final product is a β-amino-carbonyl compound also known as a Mannich base.

Explanation:

• The CSA will protonate the formaldehyde in the first step.
• The starting amine will react with the protonated formaldehyde followed by dehydration. In the next step, it undergoes a [3,3] sigmatropic reaction.
• The reaction pathway is shown below:

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• The intermediate undergoes a mannich-type reaction and gives the final product.

​Conclusion:

Hence, the major product formed in the following reaction is 
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