Dihalogenation of β-Keto Sulfides. Synthesis of α-Keto Methyl Esters and α-Keto S-Phenyl Thioesters

α-Keto esters and α-Keto S-Phenyl Thioesters are synthesized from β-keto sulfides by dihalogenation with sulfuryl chloride followed by solvolysis with methanol and acetone/water respectively.     

Synthesis of α,β-dibromo ketones by photolysis of α-bromo ketones with N-bromosuccinimide: Photoinduced β-bromination of α-bromo ketones

Irradiation of α-bromopropiophenones in the presence of NBS results in the formation of α,β-dibromopropiophenones, which can be viewed as β-bromination of α-bromopropiophenones. The reaction is believed to go through a series of reactions; photoinduced C–Br bond cleavage, elimination of HBr to give α,β-unsaturated ketone intermediates, and addition of Br₂, which are formed by the reaction between HBr and NBS. From mechanistic studies of the reaction, we have also found a very convenient method for α-debromination of the α,β-dibromopropiophenones which is by simple irradiation of the dibromo ketones in acetone or 2-propanol without the use of any additives. Our results demonstrate that bromine can be added into or eliminated from the alpha, beta, or both positions to the carbonyl group by photochemical methods, which make synthetic options of bromine containing carbonyl compounds versatile.     

Transition-Metal-Free α-Arylation of β-Keto Amides via an Interrupted Insertion Reaction of Arynes

Direct α-arylation reactions of secondary β-keto amides with arynes, generated by fluoride-induced elimination of ortho-silyl aryltriflates, are described. The transformation proceeds via an interrupted insertion reaction of arynes and leads to densely functionalized aromatic compounds exhibiting a chiral 'all carbon' quaternary center under transition-metal-free conditions. An organocatalytic asymmetric version of the reaction also proved possible, affording the proof of concept that arynes can be involved in enantioselective transformations.     

Direct Asymmetric Aldol Type Reaction with Ethyl Diazoacetate: Stereoselective Synthesis of α, β-Dihydroxy Esters

Enantioselective aldol condensation under catalytic condition remains a challenging task in modern organic synthesis, and numerous efforts have been directed to this area. In particular, the direct catalytic asymmetric aldol reaction is very attractive considering the requirement of atom efficiency. This has been studied only recently, and several very practical processes have been developed. We have recently initiated a study on the direct asymmetric aldol type reaction with ethyl diazoacetate as nucleophile. Moderate enantioselectivities (65% ～91% ee ) were achieved in the condensation of aldehydes with ethyl diazoacetate catalyzed by the chiral complex of BINOL derivatives-Zr (OBu- t )4. [1]     

Reaction of 2-aminopyridines with α, β-unsaturated acids

The reaction of 2-amino- and 2-amino-5-halopyridines with acrylic, methacrylic, and crotonic acids forms N-(2-pyridyl)- and N-(5-halo-2-pyridyl)--alanines and the betaines 2-amino-1-(2-carboxylatoethyl)pyridinium or 3,4-dihydropyrido[1,2-a]pyrimidin-2-ones, or their homologs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 80–85, January, 1992.     

Ritter Reaction with Cyclopropyl Ketones and Cyclopropyl Alcohols: Synthesis of N-Actyl- γ-Keto and N-Acyl Hohoallyl Amines

A variety of conjugated cyclopropyl ketones and cyclopropylcarbinyl alcohols were reacted with two nitriles viz. CH₃ CN and CH₂[dbnd]CH-CN in presence of cone. H₂ SO₄. It was found that with appropriate substitutions cyclopropyl ketones gave N-Acyl-γ-keto amines whereas cyclopropylcarbinyl alcohols gave the corresponding N-Acyl homoallylic amines in reasonably good yields. The olefins obtained had E-stereo-chemistry. With bicyclic cyclopropylcarbinyl alcohols the ring expanded products were formed. A plausible rationale is provided to account for these observations     

Reaction of Perfluoroalkanesulfinyl Chlorides with Enamines: A Facile Synthesis of α-Perfluoroalkanesulfinyl Ketones and Aldehydes

The reaction of perfluoroalkanesulfinyl chlorides with enamines was achieved in the presence of triethylamine, and α-perfluoroalkanesulfinyl carbonyl compounds were obtained in moderate to good yields after hydrolysis of the reaction intermediates with dilute hydrochloric acid.     

Synthesis and Reaction of 4-Methyl-3,4-epithiotetrahydropyran with α-Amino Acids

4-Methyl-3,4-epithiotetrahydropyran was synthesized by the recyclization of 4-methyl-3,4-epoxytetrahydropyran by the action of thiourea. The product reacts with -amino acids in an alkaline medium with regioselective opening of the thiirane ring at the least substituted carbon atom.     

Reaction of a chlorovinylcarbene with ketenealkyl silyl acetals. Synthesis of new α- and β-allenic carboxylates.

The reaction of ketenealkylsilylacetals with 1,1-dimethyl-2,2,3-trichlorocyclopropane in the presence of methyllithium leads to cyclopropane compounds, which, when treated with tetrabutylammonium fluoride give α- or β-allenic carboxylates.     

A Practical Synthesis of β-Keto Phosphonates from Triethyl Phosphonoacetate

An efficient and practical preparation of β-keto phosphonates, via acylation reaction of triethyl phosphonoacetate with carboxylic acid chlorides in the presence of magnesium chloride-triethylamine followed by decarbethoxylation, is described.     

Mono Halogenation of β-Keto Sulfides. Synthesis of β-Keto-α-phenylthio p-Tolyl Sulfones

β-Keto-α-Phenylthio p-Tolyl sulfones are obtained from β-keto-alkyl phenyl sulfides by halogenation with NCS followed by treatment with sodium p-toluene sulphinate.     

Hypervalent Iodine in Synthesis XXX: Palladium-Catalyzed Reaction of Diaryliodonium Salts with β-substituted-α, β-enones

The reaction of diaryliodonium salts with β-substituted-α,β-enones in the presence of a palladium catalyst affords H_β-substituted products with excellent yields.     

Direct Asymmetric α-Selective Mannich Reaction of β,γ-Unsaturated Ketones with Cyclic α-Imino Ester: Divergent Synthesis of Cyclocanaline and Tetrahydro Pyridazinone Derivatives

The first regio-, diastereo-, and enantioselective direct Mannich reaction of β,γ,-unsaturated ketones with benzoxazinone cyclic imines was enabled by Lewis acid/Brønsted base cooperative catalysis. The dinuclear zinc complex catalyzed the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, leading to corresponding adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–99 % ee range. These products were used as general intermediates in the synthesis of multisubstituted cyclocanalines, tetrahydro pyridazinones, and 4H-furo[2,3-b][1,4]benzoxazine derivatives.