Photo-irradiation of α-halo carbonyl compounds: a novel synthesis of α-hydroxy- and α,α′-dihydroxyketones

The reaction of α-halo ketones (α-iodocycloalkanones, α-bromocycloalkanones, α-iodo-β-alkoxy esters, and α-iodoacyclicketones) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketones in good yields. For α-bromoketones, it was found that α-hydroxylation does not occur. However, α-bromoketones were converted into α-hydroxyketones in the presence of KI. In the case of α,α′-diiodo ketones, α,α′-dihydroxyketones, which up to now have scarcely been reported, were obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketones.     

IODODECARBOXYLATION OF α-CARBOXYLATE, α-CINNAMOYL KETENE CYCLIC DITHIOACETALS

ABSTRACT

The iododecarboxylation reaction of α-carboxylate, α-cinnamoyl ketene cyclic dithioacetals 2 was successfully performed with iodine as halogenation reagent and in water insensitive media. This reaction provides a mild and efficient method for the preparation of α-iodo, α-cinnamoyl ketene cyclic dithioacetals 3 which are important kinds of potential new intermediates to be valued.     

Copper-Catalyzed CH Oxidation/Cross-Coupling of α-Amino Carbonyl Compounds

Keeping options open: The new and mild title reaction involving indoles selectively furnishes 1 and 2 with the aid of tert-butyl hydroperoxide (TBHP). The method represents the first example of a copper-catalyzed α?arylation of α-amino carbonyl substrates leading to α-aryl α-imino and α-aryl α-oxo carbonyl compounds using a C?H oxidation strategy.     

Polystyrene-Supported Aminocatalyst Derived from Diarylprolinol for Asymmetric α-Amination of Aldehydes

A new class of polystyrene-supported aminocatalysts with a triazole linker from diphenyl prolinol were developed. Their catalytic activity was tested in the asymmetric α-amination of aldehydes. The substrate scope of this catalysis was studied under the optimized reaction conditions. The reusability of the polystyrene-supported aminocatalyst was demonstrated up to four cycles. Based on the reaction results, a reaction mechanism was proposed for the asymmetric α-amination of aldehydes.     

Aerobic Direct Dioxygenation of Terminal/Internal Alkynes to α-Hydroxyketones by an Fe Porphyrin Catalyst

We herein report a new synthetic method for the preparation of α-hydroxyketones by the dioxygenation of alkynes. The reaction proceeds at room temperature under the action of Fe porphyrin and pinacolborane under air as a green oxidant to produce α-hydroxyketones. The mild reaction conditions allow chemoselective oxidation with functional group tolerance. Terminal alkynes in addition to internal alkynes are applicable, affording unsymmetrical α-hydroxyketones that are difficult to obtain by any reported dioxygenation of unsaturated C−C bonds.     

Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 1ère communication. Nouvelle méthode de synthèse de β-hydroxyesters

A new synthesis of β-hydroxyesters involving a reaction between a carbonyl compound, ketene and an alkyl-orthotitanate is described. The following carbonyl compounds have been studied: aldehydes, ketones, α-diketones, α- or γ-ketoesters. A reaction mechanism is proposed.     

Boroalkyl group migration provides a versatile entry into α-aminoboronic acid derivatives

A reaction exemplifying migration of boron-substituted carbon is described. We show that α-boroalkyl groups of transient boroalkyl acyl azide intermediates readily migrate from carbon to nitrogen. This process allows access to a new class of stable molecules, α-boryl isocyanates, from α-borylcarboxylic acid precursors. The methodology facilitates synthesis of a wide range of α-aminoboronic acid derivatives, including α,α-disubstituted analogues.     

OAP-H2O2-HRP伏安酶联免疫分析新体系测定人血清甲胎蛋白

本文提出邻氨基酚 (OAP)-H2O2-辣根过氧化物酶（HRP）伏安酶联免疫分析体系并用于人血清中甲胎蛋白(αFP)的测定。该方法是将HRP催化H2O 2 氧化 OAP 的酶催化反应与邻氨基酚的氧化中间产物(邻苯醌亚胺)在滴汞电极上的还原反应相偶合, 在BR缓冲溶液中, 在-0.87 V (vs.SCE) 左右产生灵敏的极谱波。根据测定标记在甲胎蛋白抗体上的HRP的量, 求得发生免疫反应的αFP的含量。该方法对甲胎蛋白测定的线性范围为1.25～400 mg/L。用所建立的方法对病人血清样品进行了测定, 并与酶联免疫吸附测定光度法(ELISA)进行对照,二者相关性很好。     

Lead(IV) acetate oxidative ring-opening of 2,3-epoxy primary alcohols: a new entry to optically active α-hydroxy carbonyl compounds

The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon-carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds.     

A short synthesis of α-allenic alcohols from α,β-unsaturated carbonyl compounds with dichloromethyl p-tolyl sulfoxide

The reaction of the α-sulfinyl carbanion of dichloromethyl p-tolyl sulfoxide with α,β-unsaturated carbonyl compounds gave 1-chlorocyclopropyl p-tolyl sulfoxides having a carbonyl group in good to high yields. The carbonyl groups in the products were reduced or treated with alkylmetals to give alcohols. Finally, the alcohols were treated with Grignard reagent to give α-allenic alcohols via the rearrangement of the cyclopropylmagnesium carbenoid intermediates, which were generated by the sulfoxide-magnesium exchange reaction, in good to high yields. This procedure provides a new method for a short synthesis of various α-allenic alcohols in two or three steps from relatively easily available α,β-unsaturated carbonyl compounds.     

α-乙酰基二硫缩烯酮α碳原子的酰化反应

进行了α-乙酰基二硫缩烯酮与酰氯的酰化反应. 以干燥的二氯甲烷为溶剂, 在四氯化钛催化下, α-乙酰基环二硫缩烯酮(1)可与脂肪及芳酰氯(2)反应, 在化合物1的α-碳原子上发生酰化反应, 以较高的产率生成各种α-乙酰基-α-酰基二硫缩烯酮(3).     

A C-C bond formation reaction at the α-carbon atom of α-oxo ketene dithioacetals via the Baylis-Hillman type reaction

The first example of TiCl₄-mediated Baylis-Hillman type reaction of α-acetyl cyclic ketene dithioacetals with arylaldehydes was described. This methodology adds a new entry to the C-C bond formation at the α-carbon atom of α-oxo ketene dithioacetals.     

Efficient synthesis of α-aryl serine derivatives via three-component reactions of aryldiazoacetates,anilines and formaldehyde

A three-component reaction based on trapping of ammonium ylides with formaldehyde was first reported. This reaction offers a new strategy for the synthesis of α-aryl serine derivatives and can be extended to the preparation of α-aryl threonine derivatives. Synthetic application of the three component reaction for the preparation of hydroquinoxaline derivative was also demonstrated.     

The Knoevenagel-Doebner reaction on 1,2-O-(2,2,2-trichloroethylidene) derivatives of D-gluco- and D-manno-furanose

The synthesis of new α,β-unsaturated furanuronic acid derivatives of α-gluco-, β-gluco- and β-manno-chloraloses via a convenient one pot procedure using the Knoevenagel-Doebner reaction approach are described. The dialdofuranose derivatives were reacted with malonic acid under Knoevenagel-Doebner reaction conditions and (E)-α,β-unsaturated furanuronic acid derivatives were obtained.     

Chemoenzymatic synthesis and application of a new,easily chiral auxiliary for the synthesis of peptidomimetics via an Ugi reaction

A new chiral auxiliary derived from α-phenylethylamine, α-(2,4-dimethoxyphenyl)ethylamine is presented. It significantly expands upon the application of α-phenylethylamine derivatives used as chiral auxiliaries. A straightforward, chemoenzymatic synthesis of non-racemic α-(2,4-dimethoxyphenyl)ethylamine is described and the new chiral auxiliary applied to an asymmetric Ugi reaction. The mild conditions used for the cleavage of the auxiliary allowed to obtain chiral, non-racemic peptidomimetics possessing reactive α,β-unsaturated double bonds.     

A new method for the preparation of functionalized unnatural α-H-α-amino acid derivatives

A new method for the preparation of α-H-α-amino acids is reported based on the α-alkylation of iminoacetic acid esters or amides. These imines are readily available by the reaction of glyoxylic acid esters with branched primary amines. The subsequent reaction with methanolic ammonia gave the corresponding iminoacetic acid amides. α-Alkylation of these imines with various electrophiles under basic conditions, followed by an acidic hydrolysis, gave α-amino acids, esters, or amides in up to 93% yield. α-Alkylation under chiral PTC conditions resulted in mono-alkylated amino acids with 90% ee.     

N-Heterocyclic carbene-catalyzed (4+2) cycloaddition/decarboxylation of silyl dienol ethers with α,β-unsaturated acid fluorides

Herein we report the first all-carbon N-heterocyclic carbene-catalyzed (4 + 2) cycloaddition. The reaction proceeds with α,β-unsaturated acid fluorides and silyl dienol ethers and produces 1,3-cyclohexadienes with complete diastereocontrol (dr >20:1) while demonstrating a new type of reaction cascade exploiting α,β-unsaturated acyl azoliums.     

Syntheses of 1-Azaazulan-2-One Analogs of Adrenergic Agents

The Friedel-Crafts reaction of 1-azaazulan-2-ones with α-haloacid chloride in the presence of aluminum trichloride gives the corresponding α-haloacyl derivatives. Treatment of these reaction products first with various secondary amines and then with sodium borohydride gives new adrenergic active amine derivatives.     

α-Alkyl(aryl)sulfenyl substituted β-ketophosphonates: synthesis, properties and reactivity

A new synthesis of the title compounds via acylation of α-lithio-α-phosphorylalkyl sulfides is described. Two additional approaches to these compounds, although less efficient, involve: (a) sulfenylation of O-silylated dialkyl β-ketophosphonates and (b) the Arbuzov reaction of triethyl phosphite with α-chloro-α-methylthiomethyl phenyl ketone. The keto-enol tautomerism of the title compounds and reactivity of the anions derived from them with electrophilic reagents were investigated. The P(O)-olefination products obtained from electron rich aromatic aldehydes were found to undergo the acid-catalyzed desulfenylation reaction affording α,β-unsaturated ketones.     

Enantioselective Diels-Alder reaction of α-(acylthio)acroleins: a new entry to sulfur-containing chiral quaternary carbons

A catalytic and enantioselective Diels-Alder reaction of α-(carbamoylthio)acroleins induced by an organoammonium salt of chiral triamine is described. α-(Carbamoylthio)acroleins are designed and synthesized as new sulfur-containing dienophiles for the first time. The Diels-Alder reaction affords chiral tertiary thiol precursors with up to 91% ee.