We get to the Robinson Annulation (and its mechanism!) near the middle of the post. First, we'll first (quickly) revisit intramolecular reactions, the Aldol Condensation, and the Michael reaction. Revisiting Intramolecular Reactions The Aldol Condensation The Intramolecular Aldol … [Read more...]
Reactions of Diazonium Salts: Sandmeyer and Related Reactions
Formation of Diazonium Salts From Aromatic Amines Today let's talk about a set of reactions of aromatic amines, that variously are catalogued under "amines" and "aromatic compounds", depending on the textbook. It involves converting an aromatic amine (NH2) into a tremendously good leaving group … [Read more...]
Aromatic Synthesis (3) – Sulfonyl Blocking Groups
I Just Want The ORTHO- Product, Thank You Question: Just how selective are ortho- para, directors for the ortho- and para- products, respectively? There are two ortho positions and one para. All else being equal, we'd expect a ratio of about 2:1 favoring the ortho. Is that what we get? … [Read more...]
Synthesis (7): Reaction Map of Benzene and Related Aromatic Compounds
Reactions of Benzene and Aromatic Compounds: A Reaction Map (PDF) Let's map out all of the reactions we've learned in this section on aromatic rings + substituents. The list comes to about 25, including the six key electrophilic aromatic substitution reactions, the Wolff-Kishner and … [Read more...]
The Strecker Synthesis of Amino Acids
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...]
Regiochemistry 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...]
Synthesis of Benzene Derivatives (2) – Polarity Reversal
In planning the synthesis of simple benzene derivatives and other 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 … [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. Synthesis 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 the Baeyer-Villiger oxidation of ketones to esters Three More Reactions Of Aromatic Substituents In this section on reactions of aromatic compounds, … [Read more...]
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