In the reaction the major product X is · ABC26OR0541
Subject: Organic Chemistry · Chapter: Organic Synthesis · Topic: Organic Synthesis – General · Exam: GATE 2000-2022 · Marks: 2 · Difficulty: Easy
In the reaction 
the major product X is
the major product X is(a)
(b)
(c)
(d)
Answer
Answer: C ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Syn D–B addition followed by protonolysis with retention makes the new D and the new H cis, so the original D ends up cis to Ph. That is option (c). The stored key (b) has H on the Ph carbon.
Explanation
Catecholborane-D adds syn across Ph–C≡C–D: D goes to the Ph-bearing carbon and B to the terminal carbon, which already carries the original D. Protonolysis of the vinylborane with CH₃COOH replaces B by H with retention of configuration. The newly added D and the new H are therefore cis, so the original D is cis to Ph: Ph(D)C=C(H)(D) with H cis to the D on the Ph carbon. Answer: (c).
Study loop for Organic Synthesis