10 Retrosynthesis and Synthesis Design Free Online FlashCards

What is retrosynthetic analysis?

Retrosynthetic analysis plans a synthesis by reasoning backward from a target to simpler precursors, then reversing the sequence to check whether each forward step is feasible.

What does a retrosynthetic disconnection represent?

A disconnection is a hypothetical bond cleavage used to simplify a target. The retrosynthetic arrow ⇒ means “could be made from,” not a reaction arrow.

How do synthons differ from synthetic equivalents?

Synthons are idealized charged fragments suggested by a disconnection. Each synthon must be matched to a real reagent, called a synthetic equivalent.

What precursors can a secondary alcohol disconnection suggest?

Disconnecting a secondary alcohol’s C–C bond can suggest an aldehyde and a carbon-nucleophile equivalent. A Grignard reagent such as R²MgBr can provide that nucleophile.

How does a Grignard reagent form an alcohol from an aldehyde?

The Grignard reagent adds to the aldehyde, forming an alkoxide; acidic work-up then gives the alcohol. Check for other groups that might react with the strongly basic, nucleophilic reagent.

What makes a bond strategic to disconnect?

A strategic bond is one whose disconnection gives simpler, recognizable fragments and corresponds to a well-established reaction.

What is a functional-group interconversion?

A functional-group interconversion changes one functional group into another without changing the carbon skeleton, such as oxidizing an alcohol to a carbonyl.

How can an FGI reveal a better route to an alcohol?

A target alcohol may be easier to construct by adding to a carbonyl than by reducing a pre-existing carbonyl. An FGI can reveal this alternative disconnection.

How does an aldol strategy form chalcone?

For chalcone, acetophenone forms an enolate that adds to benzaldehyde; dehydration of the resulting β-hydroxy ketone gives the conjugated enone.

Why is benzaldehyde a useful crossed-aldol partner?

Benzaldehyde has no α-hydrogen, so it cannot form its own enolate. This helps avoid competing self-aldol addition in the chalcone synthesis.

What three forms of selectivity should a synthesis plan assess?

Check chemoselectivity, regioselectivity, and stereoselectivity: which functional group reacts, which position reacts, and which stereoisomer forms.

When might a protecting group be necessary?

A group may react with a reagent intended for another site or alter a later reaction. A protecting group can mask it temporarily, but adds steps and should be used only when needed.