Reduction of Carboxylic Acid Derivatives Using Diphenylsilane in the Presence of a Rh–PPh3 Complex

Abstract

Reductions of carboxylic acid derivatives by silanes in the presence of rhodium complexes were studied. Carboxylic esters were reduced to alcohols by diphenylsilane catalyzed by [RhCl(cod)]2/4PPh3 or [RhCl(PPh3)3] at room temperature in up to 99% yields. For example, ethyl decanoate and ethyl phenylacetate were converted to decanol and 2-phenylethanol in 98 and 92% yields, respectively. Carboxylic acids were also reduced by this reducing system to the corresponding alcohols in high yields. Furthermore, N-monosubstituted amides were reduced to secondary amines in moderate to good yields. For sterically hindered amides, the yields were moderate, and imines were produced in competitive yields.

Selective Reduction of Carboxylic Acid Derivatives by Catalytic Hydrosilylation

“…In 2009, in parallel to our own studies, [25] Nagashima and co-workers found that [Fe(CO) 5 ] and [Fe 3 (CO) 12 ] are useful catalysts for the thermal and photoassisted reduction of tertiary amides to tertiary amines with TMDS and PMHS as reducing agents (Scheme 9).…”

“…[12] Carboxylic esters were reduced to alcohols with diphenylsilane at room temperature in up to 99 % yield. For example, ethyl decanoate and ethyl phenylacetate were converted into decanol and 2-phenylethanol in 98 and 92 % yield, respectively.…”

“…[27] As a result of our interest in the application of biorelevant metal catalysis, [28] we recently also started to explore the catalytic potential of zinc-and iron-based catalysts for the hydrosilylation of amides to amines. [29] To our delight, inexpensive and readily available iron carbonyl clusters, such as [Fe 3 (CO) 12 ], enabled the selective reduction of tertiary amides in combination with PMHS. [25] A mechanism proposed on the basis of isotopic labeling experiments is shown in Scheme 10.…”

Two Iron Catalysts are Better than One: A General and Convenient Reduction of Aromatic and Aliphatic Primary Amides

“…[13] Notably, the vast majority of the known noble metal-based catalysts can be used only for the reduction of more active tertiary or secondary amides. In fact, there is only one report by Igarashi and Fuchikami, [13b] who showed the possibility for the reduction of primary amides.…”

Selektive Reduktion von Carbonsäurederivaten durch katalytische Hydrosilylierung

“…. [12] Carbonsäureester wurden mit Diphenylsilan bei Raumtemperatur in bis zu 99 % Ausbeute zu Alkoholen reduziert. Zum Beispiel wurden Ethyldecanoat und Ethylphenylacetat in 98 % und 92 % Ausbeute zu Decanol und 2-Phenylethanol umgewandelt.…”