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: + .. - C7 Na + - Br C4 H C3

Now do the same thing for 1-propyne:

So the overall forward synthesis is a 2C + 1C + 4C coupling strategy : NaNH 2 CH 3 Br - Na + H H H C THF THF NaNH 2 Br - H CH 3 Na + C CH 3 THF THF CH 3

Now, provide a multistep synthesis of meso -5,6-decanediol from # 4C sources of carbon and any other reagents you require. CH 2 CH 2 CH 2 CH 3 H O H H O H CH 2 CH 2 CH 2 CH 3

CH 2 CH 2 CH 2 CH 3 Is a C10 vicinal diol. ˆ synthesis will involve chain elongation of an alkyne. H O H Diols are made from alkenes. Which alkene? H O H CH 2 CH 2 CH 2 CH 3 H O H H O H ( Z )-5-decene. How is ( Z )-5-decene made? From an alkyne: 5-decyne

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

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: O ? H H H acetylene heptanal One way: a 2C + 5C = 7C retrosynthetic strategy H O O is the keto form of H the enol: H H H H + Br H

Forward synthesis: NaNH 2 Br H Na H H H O 1. BH 3 @ THF H 2. H 2 O 2 , OH -

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

Forward synthesis: H 2 NaNH 2 Br H H H Na Lindlar Pd H NaNH 2 H H H H HBr H Na H Br ROOR H H O O H 2 1. O 3 H + H H H Lindlar Pd 2. Zn, H 3 O + H

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?