Solved Problems on Functional Group Synthesis

PROBLEMS

7.1. Show how you would prepare each of the following products from the given starting material. For each overall transformation indicate (1) the starting and ending functional group and (2) what change in oxidation level (if any) must be accomplished. Where more than one step is required, show each step distinctly, including reagents and conditions needed to effect the conversion

Answer:

(a) 1^◦ Alcohol → aldehyde, [O] = +2, PCC or Swern oxidation

(b) Ester → ether, [H] = −4

i. LAH

ii. NaH, CH₃l

(c) Acid → amide, no change

i. SOCl₂, DMF

ii. CH₃NHCH₂CH₃

or

i. DCC, Et₃N, CH₃NHCH₂CH₃

(d) Ketone → methylene compound, +2 → 0 [H]

i. Ph₃P=CH₂ (Wittig) or Me₃SiCH₂-Li (Peterson)

(e) 1^◦ Alcohol → aldehyde, −1 → +1, PCC or Swern oxidation

(f) Lactone → lactol (hemiacetal); +3 → +1; DIBAH, toluene, −78^◦

(g) 2^◦ Alcohol → 2^◦ amine, no change

i. H₂CrO₄, acetone

ii. CH₃NH₃, NaBH₃CN, H⁺

(h) Acid → ester, +3 → +3

i. DCC, Et₃N, EtOH

or

i. oxallyl chloride

ii. EtOH, py

(i) Alkene → alcohol; 0, −2 → +1, −3 no change

i. HgOAc₂, H₂O

ii. NaBH₄

(j) Alkene → alcohol; −1, −2 → −2, −1 no change

i. BH₃⁻THF

ii. NaOH, H₂O₂

(k) Ketone → alcohol + cyclization, +2 → 0 [O]

i. NaBH₄

ii. TsOH, benzene,

(l) Ketone → acetal; no change; HOCH₂CH₂CH₂OH, TsOH, toluene,

(m) Acid → alcohol → acetylation, +3 → −1 [H]

i. BH₃-THF

ii. Ac₂O, py, DMAP

(n) Alkene → alcohol, no change

i. HgOAc₂, H₂O

ii. NaBH₄, MeOH

(o) Ketone → α, β -unsaturated ketone; −2, −3, → −1, −2, [O]

i. LDA

ii. PhSeSePh

iii. H₂O₂

or

i. py⁻H⁺ Br⁻₃

ii. K₂CO₃

(p) 2^◦ Alcohol → acetal, 0 → +2, [O]

i. H₂CrO₄

ii. CH₃OH, H⁺, Δ

(q) trans-Alkene → alkyne; −1, −1 → 0, 0 [O]

i. Br₂, CCl₄

ii. NaNH₂

(r)

(s) Acid → amide, no change

i. DCC, Et₃N, NH₂R

or

i. oxallyl chloride,

ii. NH₂R

(t) Alcohol → ester, no change

i. ClCH₂CH₂C(O)Cl, py

(u) Alkene → alcohol, no change

i. BH₃ –THF

ii. NaOH, H₂O₂

(v) Alkyl bromide → alkene, [H]

i. NaC₂H

ii. BuLi

iii. PrBr

iv. H₂, P-2 Ni

7.2. Show two different starting materials from which you could obtain each of the following compounds. Show the reagents and conditions necessary to convert each of the starting materials into the desired product.

Answer:

7.3. Give the final products of the following reaction sequences and show the intermediate products as well. If mixtures are expected, indicate which will be the major product.

Answer: