Reactions of Aromatic Aldehydes with Boron Halides

Recently, during studies directed toward the total synthesis of the antibiotic frustulosin 1^1,2 we encountered some problems in the removal of methoxyl groups during the preparation of the phenolic aldehyde 2. Our efforts to effect this transformation led us to investigate the reactions of the boron trihalides with aromatic aldehydes. Although the methoxyl group has many desirable properties for hydroxyl protection its stability to both acids and bases often presents difficulties at the time of removal. Of the many reagents and methods devised³ for the removal of methoxyl and other alkoxyl groups boron tribromide can be considered as one of the most widely applicable reagents for this purpose. However, as a fairly powerful Lewis acid, complications can arise when acid.     

微波辐射金属铝诱发芳香醛的还原偶联反应

一系列芳香醛在Al-TiCl3-CH2Cl2体系中反应12h,以20％～70％的产率得1,2-二醇产品,相同体系中微波辐射8rain相应1,2-二醇的产率达65％～94％.微波辐射下合成1,2-二醇的优点是时间短、产率高、操作简单.     

对-甲苯乙酮与芳香醛和芳香胺的Mannich反应

Mannich反应是合成新化合物的重要方法 [1] ,其对应的产物 Mannich碱常常具有广泛的生物活性 [2 ] .文献报道 ,对 -甲苯乙酮的 Mannich碱具有抑癌 [3]和麻醉拮抗 [4 ]等生物活性 ,但是文献中对 -甲苯乙酮 Mannich碱的合成却是从胺交换法 [5] 、酮交换法 [6] 、查耳酮与胺的 Michael加成[7] 、Schiff碱与酮的缩合 [8～ 14 ] 、β-内酰胺与有机锂的亲核裂解 [15] 等间接方法得到的 .即使是从直接法合成 ,一般也是甲醛参与的 Mannich反应 .虽然芳香醛和芳香胺同时参与的 Mannich反应已有报道 [16] ,但对 -甲苯乙酮与芳香醛和芳香胺直接进行…     

Decarboxylative Mannich Reactions with N-Alkyl Imines

The use of N-alkyl imines in decarboxylative Mannich reaction with substituted malonic acids half oxyesters (SMAHOs) has been developed to afford a direct access to secondary β^2,3-aminoesters. The transformation occurs under very practical conditions (DABCO as a catalyst in bulk toluene and open to air) and can be performed with a broad range of each substrate in yields of 36 to 97 %. Importantly, the reaction was found to require the use of acidic additives in combination with the organocatalyst to limit the competitive olefination reaction.     

Reactions of Halides of Tervalent Phosphorus with Imines and -Diimines

Abstract

Isobutylidenebutylamine reacts with phosphorus trichloride in the presence of organic bases to give N-butyl-N-isobutenylamidodichloro-or bis(N-butyl-N-isobutenylamido)chlorophosphites depending on the ratio of reagents. Reasons are given in Eavour of the reaction beginning with the nucleophilic attack of the nitrogen atom of the imine on the electrondeficient phosphorus atom of the chloride. Reactions of ethyldichloro- and diethylchlorophosphites with benzylidenmethylamine produce 2-chloro- and 2-ethyl-2-oxo-1,4,2-diazaphospholanes respectively. Interaction of diethylchlorophosphite with benzylidenmethylamine in the presence of triethyphosphite results in the formation of diethyl. (N-methyl-N-α-diethylphosphonobenzylamido)phosphite. As a result of interaction of bis(diethylamino)chlorophosphine with NIN-dibutyl-2,3-butandiimine in the presence of triethylamine new compounds (2-diethylamino-1,3-dibutyl-4,5-dimethyl-1,3,2-diazaphospholane and 4,8-dibutyl-3,7-bis(diethylamino)-[3.3.01-bicyclooctadiene-l15) are obtained. The structure of the latter is proved by means of ¹H, ³¹ p NMR-spectroscopy, and a complete X-ray analysis. Alkyldichlorophosphines form phosphonium salts of 1,3,2-diazaphospholene structure with a-diimines and 2-chloro-1,3-dicyclohexyl-4-chloro-1,3,2-diazaphospholene resulting from the reaction of N,N-dicyclohexylethylenediimine with PCl₃. In this product the P-C1 bond is unusually long, which is confirmed by X-ray analysis. In the course of the interaction of tervalent phosphorus halides with α,β-unsaturated imines a new reaction has been discovered with the formation of 1,2-dihydro-1,2-azaphosphorines.     

Highly meso-Diastereoselective Pinacol Coupling of Aromatic Aldehydes Mediated by Al Powder/Copper Sulfate in Water

Pinacol-type coupling reaction products presenting a high meso-diastereoselectivity (the ratio dl/meso was 4/96 up to 1/99) were obtained in fair to good yields (24–69%) using several aromatic aldehydes as starting materials and aluminium powder/copper sulfate as catalysts, in water, under reflux conditions.     

超声波辐射下金属锰引发芳香醛的偶联反应

超声波引发下Mn-H2O-HOAc体系中进行的一系列芳香醛的偶联反应,室温反应3 h得到45%～71%的邻二醇产品.     

Cross‐Electrophile Coupling of Vinyl Halides with Alkyl Halides

An improved method for the reductive coupling of aryl and vinyl bromides with alkyl halides that gave high yields for a variety of substrates at room temperature with a low (2.5 to 0.5 mol %) catalyst loading is presented. Under the optimized conditions, difficult substrates, such as unhindered alkenyl bromides, can be coupled to give the desired olefins with minimal diene formation and good stereoretention. These improved conditions also worked well for aryl bromides. For example, a gram‐scale reaction was demonstrated with 0.5 mol % catalyst loading, whereas reactions at 10 mol % catalyst loading completed in as little as 20 minutes. Finally, a low‐cost single‐component pre‐catalyst, (bpy)NiI₂ (bpy=2,2′‐bipyridine) that is both air‐ and moisture‐stable over a period of months was introduced.     

Reactions of β-Pinene with Aromatic Aldehydes

Aromatic aldehydes add to β-pinene under Lewis acid catalyzed Prins reaction conditions and yield the corresponding homoallylic alcohols. The reactions proceed in poor yield when electron donating substituents are present on the aromatic ring.     

Reactions of Verbenone Dienolate with Aromatic Aldehydes

Lithium dienolate of verbenone reacts with aromatic aldehydes to give α- and γ-aldols. Unusual features of the reaction include: selective formation of the γ-aldols under kinetic conditions, absence of deconjugated α-products, high sensitivity to electronic effects and formation of bis-aldols 5.     

超声波作用下锌粉诱发芳香醛的还原偶联反应

超声波作用下,芳香醛在Zn-10％NaOH(aq．)-bleOH体系中反应,室温下25min～60min内得到41％～97％的偶联产物邻二醇。     

铝-碱金属氟化物在超声辐射下于水中诱发的芳香醛还原偶联

超声辐射下, 铝粉在氟化钾或氟化钠的水溶液中, 可使芳香醛快速还原或偶联, 生成相应的双分子还原偶联产物和少量单分子还原产物, 其中还原偶联产物邻二醇的收率达15%～82%.     

Reactions of Polysaccharide Aldehydes with Aromatic Hydroxy Compounds

Reaction of dextran polyaldehyde with phenol or its derivatives was suggested as a way to modify polysaccharides with aromatic hydroxy compounds.     

Metal‐Catalyzed Reductive Coupling Reactions of Organic Halides with Carbonyl‐Type Compounds

Metal‐catalyzed reductive coupling reactions of aryl halides and (pseudo)halides with carbonyl‐type compounds have undergone an impressive development within the last years. These methodologies have shown to be a powerful alternate strategy, practicality aside, to the use of stoichiometric, well‐defined, and, in some cases, air‐sensitive organometallic species. In this Minireview, the recent findings in this field are summarized, with particular emphasis on the mechanistic interpretation of the results and future aspects of this area of expertise.     

Highly Efficient Organosuperbase-Catalyzed Mannich-type Reactions of Sulfonylimidates with Imines: Successful Use of Aliphatic Imines as Substrates and a Unique Reaction Mechanism

First walk, then run! Highly efficient organosuperbase-catalyzed Mannich-type reactions of sulfonylimidates with readily prepared Boc-protected imines have been developed. The desired products were obtained in high yield and with high anti selectivity. Mechanistic studies show an induction period for the catalyzed reaction, and that the organosuperbase works as an initiator.     

Catalytic Reductive Cross-Coupling between Aromatic Aldehydes and Arylnitriles

A reductive cross-coupling reaction between aromatic aldehydes and arylnitriles using a copper catalyst and a silylboronate as a reductant is reported. This protocol represents an unprecedented approach to the chemoselective synthesis of α-hydroxy ketones by electrophile–electrophile cross-coupling.     

超声辐射下低价钛配合物诱发芳香醛的还原偶联

超声辐射下，于二氯甲烷溶剂中，以锌粉或铝粉还原四氯化钛的四氢呋喃配合 物可生成相应的低价钛配合物，室温下此配合物可使一些芳香醛在4～25 min内还 原偶联为相应的邻二醇，收率为33％～98％．     

纯水中金属钕诱发芳香醛烯丙基化反应的研究

在Nd-SnCl₂-H₂O体系中, 用烯丙基溴超声诱发下进行了一系列芳香醛的烯丙基反应, 室温反应50～60 min得76%～93%烯丙基化产物; 而不用超声波时同样体系中搅拌3～4 h高烯丙基醇产率为30%～86%. 该方法时间短、产率高、环境友好.     

芳香醛与丙二酸亚异丙酯的固相缩合反应

二甲基芳亚甲基二氧六环二酮;芳香醛与丙二酸亚异丙酯的固相缩合反应     

Gallium-induced Barbier coupling of carbonyl compounds with allyl iodide

Gallium metal readily prompted the allylation of aldehydes and ketones with allyl iodide. α, β-Unsaturated carbonyl compounds underwent only 1,2-addition.