Synthesize 2-heptyne from acetylene (ethyne) and any haloalkanes you - - PowerPoint PPT Presentation

Synthesize 2-heptyne from acetylene (ethyne) and any haloalkanes you need

Retrosynthesis:

Br H C7 ..

• +
• Na+

C4 C3

Now do the same thing for 1-propyne:

So the overall forward synthesis is a 2C + 1C + 4C coupling strategy:

H H C H H CH3 C CH3 Br CH3 NaNH2 THF

• Na+

THF CH3Br NaNH2 THF

• Na+

THF

Now, provide a multistep synthesis of meso-5,6-decanediol from # 4C sources of carbon and any other reagents you require.

CH2CH2CH2CH3 H O H H O H CH2CH2CH2CH3

Is a C10 vicinal diol. ˆ synthesis will involve chain elongation of an alkyne. Diols are made from alkenes. Which alkene?

(Z)-5-decene.

How is (Z)-5-decene made? From an alkyne: 5-decyne

CH2CH2CH2CH3 H O H H O H CH2CH2CH2CH3 H O H H O H

Finally, how is this alkyne created from pieces of 4 carbons or fewer? So this is a 2C + 4C + 4C = 10C assembly strategy.

Br Br + +

The forward synthesis of meso-5,6-decanediol is: . . .How would a synthesis of (SR, SR)-5,6-butanediol differ from the one just proposed?

Synthesize heptanal from acetylene, # 5C compounds, and any other reagents required:

acetylene

heptanal One way: a 2C + 5C = 7C retrosynthetic strategy

H O H H ?

H O H O H H H Br H H is the keto form of the enol: +

Forward synthesis:

H O H H H Br Na H NaNH2

• 1. BH3 @ THF
• 2. H2O2, OH-

A second strategy: a [(2C + 4C) + 2C] - 1C = 7C approach

H O H H H H Br H H H H H H Br H H + +

Forward synthesis:

H O H H H Br Na H H H H Br H H Na H H H H H H H O NaNH2 H2 Lindlar Pd HBr ROOR NaNH2 H2 Lindlar Pd

• 1. O3
• 2. Zn, H3O+

+

Using the general strategy of our second synthesis, can you think of a third way that makes heptanal without generating any other aldehydes as side-products?