1072. A general synthesis of ethers

Abstract

Hydrogenation of ketones in presence of platinum oxide in alcoholic acid leads to ethers with good yields.THE reaction COR1R2 + R30H R1R2CH*OR3 seems generally to occur on hydrogenation in alcoholic acid in presence of platinum. A variety of ketones and also an aldehyde have been tested (see Table 1) and have given reasonable to excellent yields. As side products, the alkane and alcohol related to the carbonyl compound are also formed, in yields varying greatly according to the conditions. Possible intermediates are the hemiketal, R1R2C(OH)*OR3, the ketal, R1R2C(OR3),, and the enol ether R2*CH:CR1*OR3, the first seeming to be the most likely. TABLE 1. Yields of ethers obtained in presence of alcohols.*

Catalytic Reductive Alcohol Etherifications with Carbonyl‐Based Compounds or CO2 and Related Transformations for the Synthesis of Ether Derivatives

“…Thus, H 2 has been studied as a clean reducing agent in reductive couplings between alcohols and carbonyl compounds, mainly catalyzed by heterogeneous systems, which is an additional advantage from the sustainability point of view, although some homogeneous catalysts have been also described [1e,g,h] . From the heterogeneous field, in 1963 Anteunis and co‐workers described the first example of a reductive etherification between alcohols and carbonyl compounds employing H 2 (Scheme 9A) [87] . In this work, authors make use of Adam's catalyst PtO 2 to perform the reductive coupling of aliphatic carbonyl substrates using the alcohol as solvent, at RT and 1 bar of H 2 .…”

“…[ 1e , 1g , 1h ] From the heterogeneous field, in 1963 Anteunis and co‐workers described the first example of a reductive etherification between alcohols and carbonyl compounds employing H 2 (Scheme 9 A). [87] In this work, authors make use of Adam's catalyst PtO 2 to perform the reductive coupling of aliphatic carbonyl substrates using the alcohol as solvent, at RT and 1 bar of H 2 . Unfortunately, strong acidic conditions were required for acetalization steps.…”

Internal Addition of Ketocarbenes to Conjugated Double Bonds

“…From this we assume that the carbonyl group was reduced to a methyl ether (Vc), presumably via a hemiketal derived from the solvent (methanol). It is known that hemiketal formation is particularly facile from a keto group situated at a one-carbon bridge in strained systems [26] and there are a number of examples of the hydrogenolysis of hemiketals and lactols [27] , as well as the direct hydrogenation of ketones in alcohols, to ethers [28,29]. EXPERIMENTAL Melting points are uncorrected.…”

Reductive Etherification of Aldehydes and Ketones with Alcohols and Triethylsilane Catalysed by Yb(OTf)3: an Efficient One‐Pot Benzylation of Alcohols

“…Catalytic hydrogenation of aldehydes and ketones in alcoholic acidic media appears to provide the most general and convenient route to symmetrical and unsymmetrical ethers (Figure e). However, hydrocarbon formation competes with ether production, and yields are low when aldehydes are reduced or when the alcohol used is larger than propyl …”