Laboratory synthesis carbonyl halides

The first reaction provides a route for the reduction of alkyl halides since the carbo-cation (isopropyl, in Rl) may be prepared from action of AICI3 on the corresponding alkyl halide. Reactions of the type Rl are also important in the process, catalytic cracking, in the manufacture of gasoline. They have also been studied in mass spectro-metric experiments [235]. Reaction R2 is one route to the preparation of carbocations under stable ion conditions. Reaction R3 is employed in the laboratory synthesis of the tropylium cation. Reaction R4, the (crossed) Cannizzaro reaction, is unusual in that it takes place under strongly basic conditions. The oxy dianion is an intermediate in the reaction of concentrated hydroxide with the aldehyde, R HO. None of R1, R2, or R3 may have hydrogen atoms a to the carbonyl groups. Formaldehyde (R1 = H) is readily... 

Among the carbonylation reactions of aryl halides, those of heteroaryl halides were of special interest to industrial research groups. The attachment of carbonyl functionalities onto heterocyclic frameworks by replacing a halide substituent provides an easy access to valuable intermediates for the manufacture of antifibrotics, herbicides, and other pharmaceuticals. Hence, this type of carbonylation reaction has been used for the production of Lazabemide, a monoamine oxidase B inhibitor, from conunercially available 2,5-dichloropyridine. The original eight-step laboratory synthesis of Lazabemide was replaced by a one-step protocol (Scheme The product Lazabemide was iso-... 

Two different approaches are commonly used for the synthesis of alkynes. In the first, an appropriate electrophile undergoes nucleophilic attack by an acetylide ion. The electrophile may be an unhindered primary alkyl halide (undergoes Sn2), or it may be a carbonyl compound (undergoes addition to give an alcohol). Either reaction joins two fragments and gives a product with a lengthened carbon skeleton. This approach is used in many laboratory syntheses of alkynes. 

One of the oldest and best known carbonyl alkylation reactions in the laboratory is the malonic ester synthesis, a method for preparing a carboxylic acid from an alkyl halide while lengthening the carbon chain by two atoms. 

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