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multistep synthesis guide 1 2 3 4 5 > tutorials > home      

4. Making your life easier: Sorting your synthetic tools

There are pretty much two types of synthetic tools available to you: (1) carbon-carbon bond forming reactions, and (2) functional group reactions that convert one functional group into another (like a reaction that converts an alcohol into a ketone, for example).

You may have noticed that many, many multistep syntheses involve making carbon-carbon bonds (which, in turn, you will have noticed by comparing the carbon skeleton of the starting material and product as suggested in a previous tip). In the toolbox of all your reactions, these carbon-carbon bond forming reactions should go right on the top where they are easy to reach. The functional group transformations are of more secondary importance and go on the bottom of the toolbox to be dusted off when needed.

synthetic toolbox
Synthetic toolbox.

Step 1: Compiling a list of all the carbon-carbon forming reactions you've learned.

Carbon-carbon reactions are your primary tools to build up your molecules, and are perhaps the most important and valuable reactions to remember. Once you know which carbon-carbon reactions to use to make the product, the other reactions often seem to magically fall into place.

At first, your list of carbon-carbon forming reactions will be small. But this list will get bigger. At the end of your first semester, you may have a list that contains some of the following carbon-carbon reactions (and perhaps others, depending on what material your professor and textbook chooses to cover):

Your most important synthetic tools: Carbon-carbon forming reactions

  • Acetylide reactions. These reactions involve use of an acetylide (a deprotonated terminal alkyne) as a nucleophile. Typically, the acetylide is used to attack a primary halide (in an SN2 reaction) or a carbonyl group to make an alcohol.

    acetylide chemistry

  • Cyanide additions to primary halides. Cyanides can be substituted for halides in a SN2 or SN1 substitution reaction (although I'd recommend you stick with SN2 reactions rather than SN1 reactions in your multistep syntheses).

    cyano addition

  • The Wittig Reaction. Makes a carbon-carbon double bond starting with a carbonyl compound phosphonium ylide

  • Friedel-Crafts reactions (for aromatic rings). This reaction makes an aromatic-carbon bond.

  • Diels-Alder reaction. This reaction takes a diene and a dienophile to make ringed and bicyclic products. This reaction makes two new carbon-carbon bonds.

    Diels-Alder reaction
  • Grignard reaction. This reaction adds a halomagnesium reagent (Grignard reagent) to a carbonyl to make an alcohol.

    Grignard reaction
Some common carbon-carbon forming reactions in first-semester undergraduate organic chemistry

Later (second semester typically), you may add enolate and enol reactions to the list (like the aldol reaction, Claisen reaction, Michael reaction, etc).

 Continue Tutorial :: Incorporating carbon-carbon reactions into your retrosyntheses

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