The Strecker synthesis is a two-step procedure for the synthesis of amino acids. It begins with the addition of cyanide ion to an imine, forming an alpha-amino nitrile. This is then hydrolyzed (e.g. with strong acid) to give an alpha-amino acid. By varying the R group on the imine, a wide variety of … [Read more...]
Regioselectivity In The Diels-Alder Reaction
When non-symmetrical dienes react with non-symmetrical dienophiles, two regioisomers are possible. Dienes with substituents on the terminus ("1-substituted dienes") tend to give "1,2" products ("ortho"). Dienes with substituents on the 2-position ("2-substituted dienes") tend to give the "1,4" … [Read more...]
The Ruff Degradation and Kiliani-Fischer Synthesis
The Kiliani-Fischer Synthesis is a method for extending a carbohydrate chain by a single carbon. The Ruff Degradation is a method for shortening a carbohydrate chain by a single carbon. The Kiliani-Fischer Synthesis involves addition of cyanide ion to an open-chain aldehyde (in the case of … [Read more...]
Aromatic Synthesis (2) – Polarity Reversal
In planning the synthesis of simple aromatic compounds, it's vital to know some tricks for changing ortho-, para- directors into meta- directors, and vice versa! Here we go into detail on how to do these "reversals of polarity". Visual summary: Last time we talked about the importance of … [Read more...]
Aromatic Synthesis (1) – “Order Of Operations”
When planning a synthesis of simple aromatic compounds, it's not enough to pick the right reactions. You also have to put them in the right order! If you're not careful, you may end up making a para- product when you meant to make a meta- , or vice versa! More detail below. Why "Order Of … [Read more...]
More Reactions on the Aromatic Sidechain: Reduction of Nitro Groups and the Baeyer Villiger
Here we cover three new reactions of aromatic substituents: reduction of nitro groups to amines, protection of amines as amides, and on the Baeyer-Villiger reaction of ketones: Three More Reactions Of Aromatic Substituents In this section on reactions of aromatic compounds, we've … [Read more...]
The Retro Diels-Alder Reaction
In the last post in this series on the Diels-Alder [See: Diels-Alder Reaction: Kinetic and Thermodynamic Control] we saw that if you apply enough heat, the Diels-Alder can operate in both the forward and reverse directions! The "retro-Diels Alder" reaction is the exact reverse of the … [Read more...]
The Cope Elimination
The "Cope Elimination" is a reaction where an amine is oxidized to an intermediate called an "N-oxide", which, when heated, acts as the base in an intramolecular elimination reaction. Treating a tertiary amine (which itself can be created through reductive elimination, for instance) with … [Read more...]
Nucleophilic Aromatic Substitution (2) – Arynes
In this post we'll discuss nucleophilic aromatic substitution, but with a new twist; a nucleophilic aromatic substitution that passes through a strange-looking intermediate called an aryne. Previously [see: Nucleophilic Aromatic Substitution] we saw that electron-poor aromatic rings containing a … [Read more...]
Classification of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers
Classification of Isomers Given that this is a long post, here's a quick index. The concept of how molecules can be "related" Non-isomers versus isomers Constitutional isomers versus stereoisomers Enantiomers versus 'non-enantiomers' (a.k.a. diastereomers) Diastereomers are … [Read more...]
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