Ruthenium hydride-catalyzed addition of aldehydes to dienes leading to beta,gamma-unsaturated ketones

An efficient cross-addition reaction of dienes with aldehydes was developed by using RuHCl(CO)(PPh3)3 as a catalyst to give a wide variety of beta,gamma-unsaturated ketones, where a pi-allylruthenium species, derived from hydroruthenation of diene, may be involved as a key intermediate.     

Direct conversion of N-methoxy-N-methylamides (Weinreb amides) to ketones via a nonclassical Wittig reaction

[reaction: see text] N-Methoxy-N-methylamides (Weinreb amides) are converted efficiently into ketones by reaction with alkylidenetriphenylphosphoranes and in situ hydrolysis of the product.     

Diene hydroacylation from the alcohol or aldehyde oxidation level via ruthenium-catalyzed C-C bond-forming transfer hydrogenation: synthesis of beta,gamma-unsaturated ketones

Under the conditions of ruthenium-catalyzed transfer hydrogenation, isoprene couples to benzylic and aliphatic alcohols 1a-g to deliver beta,gamma-unsaturated ketones 3a-g in good to excellent isolated yields. Under identical conditions, aldehydes 2a-g couple to isoprene to provide an identical set of beta,gamma-unsaturated ketones 3a-g in good to excellent isolated yields. As demonstrated by the coupling of butadiene, myrcene, and 1,2-dimethylbutadiene to representative alcohols 1b, 1c, and 1e, diverse acyclic dienes participate in transfer hydrogenative coupling to form beta,gamma-unsaturated ketones. In all cases, complete branch regioselectivity is observed, and, with the exception of adduct 3j, isomerization to the conjugated enone is not detected. Thus, formal intermolecular diene hydroacylation is achieved from the alcohol or aldehyde oxidation level. In earlier studies employing a related ruthenium catalyst, acyclic dienes were coupled to carbonyl partners from the alcohol or aldehyde oxidation level to furnish branched homoallylic alcohols. Thus, under transfer hydrogenative coupling conditions, all oxidation levels of substrate (alcohol or aldehyde) and product (homoallyl alcohol or beta,gamma-unsaturated ketone) are accessible.     

Alkynyl derivatives of selenophene II. Addition of thiols to selenienyl alkynyl ketones

The reaction of selenienyl alkynyl ketones with thiophenol and butyl mercaptan gave good yields of selenienylketovinyl sulfides. The corresponding sulfones were obtained from some of the sulfides by oxidation with hydrogen peroxide. The IR spectra of the synthesized compounds are discussed.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1637–1639, December, 1971.     

Asymmetric transformations of acyloxyphenyl ketones by enzyme-metal multicatalysis

A multipathway process comprising several enzyme- and metal-catalyzed reactions has been explored for the asymmetric transformations of acyloxyphenyl ketones to optically active hydroxyphenyl alcohols in the ester forms. The process comprises nine component reactions in three pathways, all of which take place by the catalytic actions of only two catalysts, a lipase and a ruthenium complex. The synthetic reactions were carried out on 0.2-0.6 mmol scales for eight different substrates under an atmosphere of hydrogen (1 atm) in toluene at 70 degrees C for 3 days. In most cases, the yields were high (92-96%) and the optical purities were excellent (96-98% ee), This work thus has demonstrated that enzyme-metal multicatalysis has great potential as a new methodology for asymmetric transformations.     

Direct access to ketones from aldehydes via rhodium-catalyzed cross-coupling reaction with potassium trifluoro(organo)borates

A direct cross-coupling reaction of aromatic aldehydes with potassium trifluoro(organo)borates afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst and acetone. This new reaction, involving a formal aldehyde C-H bond activation, is believed to proceed via a Heck-type mechanism followed by hydride transfer to acetone.     

Direct entry to peptidyl ketones via SmI2-mediated C-C bond formation with readily accessible N-peptidyl oxazolidinones

In this work, a new method for the preparation of peptidyl ketones is presented employing a SmI(2)/H(2)O-mediated coupling of N-peptidyl oxazolidinones with electron-deficient alkenes. The requisite peptide imides were easily prepared by solution-phase peptide synthesis starting from an N-acyl oxazolidinone derivative of an amino acid. Importantly, they could be used directly in the C-C bond-forming step without the need for further functionalization. Coupling of these peptide derivatives with a second peptide possessing an N-terminal acryloyl group leads to ketomethylene isosteres of glycine-containing peptides. This method represents an alternative means for ligating two small peptides through a C-C bond-forming step.     

Direct L-proline-catalyzed asymmetric alpha-amination of ketones

The first direct catalytic asymmetric alpha-amination of ketones catalyzed by l-proline has been developed. The reactions proceed with various azodicarboxylates as the nitrogen source in high yields and excellent enantioselectivities (up to 99% ee). The scope and potential of the reaction are demonstrated by further transformation of the alpha-hydrazino ketones formed to both optically active syn and anti-alpha-amino alcohol derivatives.     

Direct formation of functionalized ketones via the coupling of functionalized organocopper reagents with acid chlorides

Highly reactive copper solutions have been prepared by the lithium naphthalide reduction of a copper(I) iodide/triphenyl-phosphine complex. These copper solutions react rapidly with functionalized alkyl halides to give organocopper reagents which have been effectively trapped with acid chlorides giving functionalized ketones in good yields. Ester, nitrile, chloride, remote epoxide, and, to some degree, ketone groups can be tolerated by this approach.     

Synthesis of functional derivatives of aryl trichlorovinyl (trichloroallyl) ketones via consecutive transformations of the carbonyl group

An efficient procedure have been developed for the selective reduction of the carbonyl group in phenyl trichlorovinyl ketone and aryl trichloroallyl ketones by the action of NaBH₄ in propan-2-ol to obtain the corresponding alcohols. The hydroxy group in the latter was converted into amino by the Ritter reaction. Treatment of the alcohols and amines with 5-phenylisoxazole-3-carbonyl chloride and 4,5-dichloroisothiazole-3-carbonyl chloride gave the corresponding esters and amides, and condensation of the amines with aromatic aldehydes afforded Schiff bases.     

Direct conversion of thiols and disulfides into sulfonamides

The H₂O₂-ZrCl₄ reagent system is used as a new and efficient reagent for the conversion of thiols and disulfides into sulfonamides. The protocol offers several advantages such as excellent yields of products and extremely fast reactions at room temperature. The reagent system is very easy to handle and is environmentally safe and economical.     

Direct conversion of primary and secondary carboxylic acids to trifluoromethyl ketones

Primary and secondary carboxylic acids were converted in one step to the corresponding trifluoromethyl ketones by treatment with trifluoroacetic anhydride (TFAA) and pyridine in toluene at 60-100 °C followed by hydrolysis/decarboxylation with water at 45 °C.     

Direct α-hydroxylation of ketones using iodosobenzene

Ketones are converted smoothly into the corresponding acyloin with a high degree of selectivity upon treatment with iodosobenzene or phenyliodosodiacetate in methanolic sodium hydroxide.