Synthesis of aldehydes and secondary amines from carboxylic acids via imines

Scalable Birch reduction with lithium and ethylenediamine in tetrahydrofuran

“…Arenes could be reduced to the Birch-type products with lithium in a mixture of methylamine and isopropanol, but overreduction appeared inevitable ( 18 ). Benzoic acid was reduced to benzaldehyde in 25% yield in the presence of lithium, methylamine, and ammonium nitrate ( 19 ). The benefit of ethylenediamine as a solvent for dissolving metal reductions was also demonstrated by others ( 20 ).…”

Selective Reduction of Carboxylic Acids to Aldehydes Catalyzed by B(C6F5)3

“…One of the potentially most useful routes involves direct reduction of carboxylic acids to aldehydes via hydrogenation (eq 1, Scheme ); however, high pressures and temperatures are required which makes control of the chemoselectivity difficult due to the ready reduction of aldehydes to alcohols . Alternatively, direct transformation from carboxylic acids to aldehydes has been accomplished by using strong reducing agents which include lithium in methylamine, alane, thexylborane, i -BuMgBr in combination with a titanocene catalyst, and activated amino-silanes (eq 2) . A two-step procedure is usually preferred, involving the transformation of carboxylic acids to more reactive acid derivatives, followed by hydrogenation or hydride reduction reactions (eq 3) .…”

Ruthenium Chloride Catalyzed One-Pot Synthesis of Aldehydes Directly from Benzylic or Primary Alkyl Halides in Aqueous Medium

“…The aldehyde group is one of the most important functional groups in the field of synthetic organic chemistry, and is widely employed in the pharmaceutical, pesticide, dye, perfumery, agrochemicals, flavoring agents, and spice sectors. 1 Aldehydes also act as starting materials for making several other valuable products such as carboxylic acids, 2 Schiff bases, 3 or imines. 4 As a result, a plethora of methods are available in the literature for the synthesis of aldehydes.…”