Question

Question. Give the structures of the intermediates represented by letters in this synthesis.

Short answer

Methyl-3-phenylpropanoate undergoes reduction with lithium aluminum hydride and during this process, ester group gets converted to alcoholic group and formation of J product occurs. Further, on treatment with tosyl chloride in presence of pyridine, hydroxyl group gets converted to good leaving group, that is, tosylate and product L forms. Product L on treatment with bulky base such as potassium tert.butoxide gives product M in which alkene is formed.

Further, on treatment with bromine in presence of water as nucleophile, bromonium ion forms and water attacks from the opposite plane to which bromonium ion is formed. Product N gets formed in which bromine and hydroxyl are trans to each other. Product J on oxidation with TEMPO reagent gives product K in which aldehyde is formed.

Formation of products J, K, L, M and N

Step-by-step solution

Step-1. Formation of products J, K, L, M, N:

Methyl-3-phenylpropanoate undergoes reduction with lithium aluminum hydride and during this process, ester group gets converted to alcoholic group and formation of J product occurs. Further, on treatment with tosyl chloride in presence of pyridine, hydroxyl group gets converted to good leaving group, that is, tosylate and product L forms. Product L on treatment with bulky base such as potassium tert.butoxide gives product M in which alkene is formed.

Further, on treatment with bromine in presence of water as nucleophile, bromonium ion forms and water attacks from the opposite plane to which bromonium ion is formed. Product N gets formed in which bromine and hydroxyl are trans to each other. Product J on oxidation with TEMPO reagent gives product K in which aldehyde is formed.

Formation of products J, K, L, M and N

Step-2. Formation of products O, P, Q:

Product N on treatment with TIPS-Cl, which acts as a protecting group of hydroxyl and triethylamine as base gets converted to product O, in which hydroxyl group is protected. Further, on treatment with Grignard reagent, that is magnesium in presence of ether, product P forms which on reaction with product K forms product Q. Reaction between carbonyl group and Grignard reagent which forms product Q which on further reaction with Bu₄NF which is deprotecting group of hydroxyl forms the final product.

Formation of products O, P and Q