Eine cyclische Methylendiphosphinsäure: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ5,3λ5‐[1,3]diphosphinin

A Cyclic Methylenediphosphinic Acid: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ⁵,3λ⁵‐[1,3]diphosphinine Strong acids protonate 1,3‐bis(dimethylamino)‐1λ⁵,3λ⁵‐[1,3]diphosphinine ( 5 ) to give the corresponding cation. The protonation is followed by hydrolytic cleavage of the dimethylamino groups resulting in the formation of the cyclic methylenediphosphinic acid ( 6 ).     

New Approaches to the Synthesis of 4‐(2‐Aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones and 3‐Ureidoindoles and a Study of Their Interconversion

3‐Alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones ( 2 ) and 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) react in boiling concentrated HCl to give 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ). The same compounds were prepared by the same procedure from 2‐alkyl/aryl‐3‐ureido‐1H‐indoles ( 4 ), which were obtained from the reaction of 3‐alkyl/aryl‐3‐aminoquinoline‐2,4(1H,3H)‐diones ( 1 ) with 1,3‐diphenylurea or by the transformation of 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) and 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ) in boiling AcOH. The latter were converted into 1,3‐bis[2‐(2‐oxo‐2,3‐dihydro‐1H‐imidazol‐4‐yl)phenyl]ureas ( 5 ) by treatment with triphosgene. All compounds were characterized by ¹H‐ and ¹³C‐NMR and IR spectroscopy, as well as atmospheric pressure chemical‐ionisation mass spectra.     

Stereoselective Synthesis of 1,3-Enynylstannanes via Palladium Catalyzed Cross-Coupling Reactions of （Z）-α-Bromovinylstannanes

Based on the different reactivity of stannyl and bromo groups, (Z)-α-bromovinylstannanes can undergo the cross-coupling reaction with alkynyl Grignard reagents in the presence of tetrakis(triphenylphosphine)palladium(0) catalyst in THF at room temperature to afford stereoselectively 1,3-enynylstannanes in good yields.     

Formal Synthesis of Natural 1,3‐Polyol/α‐Pyrone Diastereoisomers

A stereoselective formal synthesis of diastereoisomers of 1,3‐polyol/α‐pyrone antifungal natural products isolated from Ravensara anisata has been achieved involving epoxide opening and asymmetric allylation as key steps.     

Toward the Synthesis of Modified Carbohydrates by Conjugate Addition of Propane‐1,3‐dithiol to α,β‐Unsaturated Ketones

Selected 5‐substituted derivatives 4 of 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one were treated with propane‐1,3‐dithiol under various conditions. The unprotected hydroxy ketones underwent cyclization during the dithiol addition and gave the corresponding 3‐(diethoxymethyl)‐2‐oxa‐6,10‐dithiaspiro[4.5]decan‐3‐ols 5 in 80–90% yield as the only products (Scheme 3 and Table 1). These products can be regarded as partly modified carbohydrates in the furanose form. When the benzyl‐protected analogues 10‐Bn of the 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one derivatives were treated with the same dithiol, however, no cyclization occurred; instead the corresponding 3‐{2‐[(benzyloxy)methyl]‐1,3‐dithian‐2‐yl}‐1,1‐diethoxypropan‐2‐one derivatives 11‐Bn were formed in good yield (up to 99%; Table 4). These 1,3‐dithianes were and are in the process of being converted to a number of new carbohydrate analogues, and here are reported high‐yield syntheses of functionalized molecules 17 belonging to the 5,5‐diethoxy‐1,4‐dihydroxypentan‐2‐one family of compounds (Table 7), via 15‐Bn (Table 5) and 16‐Bn (Table 6 and Scheme 8).     

NaHCO3‐Catalyzed Hihgly Regiospecific Aminobromination of ß,ß‐Dicyanostyrene Derivatives with 1,3‐Dibromo‐5,5‐dimethylhydantoin (DBDMH)

The aminobromination of β,β‐dicyanostyrene derivetives with 1,3‐dibromo‐5,5‐dimethylhydantoin (DBDMH) has been systematic studied. The reaction afforded the vicinal haloamino products in good to excellent yields at room temperature (the highest yield was up to 94 %), and the full regiospecificity of all products were achieved catalyzed by NaHCO₃ in CH₃CN. A possible pathway involving a Michael Addition reaction for this aminobromination was proposed.     

Reactions of Acid Chlorides/Ketenes with 2‐Substituted 4,5‐Dihydro‐4,4‐dimethyl‐1,3‐thiazoles: Formation of Penam Derivatives

Addition reactions of acid chlorides with various 2‐substituted 4,5‐dihydro‐4,4‐dimethyl‐5‐(methylsulfanyl)‐1,3‐thiazoles under basic conditions were studied. Two kinds of products were obtained from these additions, β‐lactams and non‐β‐lactam adducts. When the reaction was carried out with 4,5‐dihydro‐1,3‐thiazoles with a Ph substituent at C(2), the reaction proceeded via formal [2+2] cycloaddition and led to the correspoding β‐lactam. On the other hand, acid chlorides and 4,5‐dihydro‐1,3‐thiazoles bearing an α‐H‐atom at the C(2)‐substituent underwent C(α)‐ and/or N‐addition reactions and furnished non‐β‐lactam adducts, i.e., C(α)‐ and/or N‐acylated 1,3‐thiazolidines. The attempted transformations of sulfonyl esters of exo‐6‐hydroxy penams to endo‐6‐azido penams failed, although they were successful with mono‐β‐lactams under the same conditions.     

Unexpected Spiroproducts from the Reaction of N‐Benzoylglycine with Ortho‐Formylbenzoic Acids −3,5′‐Dioxo‐2′‐Phenyl‐1,3‐Dihydrospiro[Indene‐2,4′‐[1,3]Oxazol]‐1‐yl Acetates: Establishments of Their Structure

This paper describes a method of preparation of new 3,5′‐dioxo‐2′‐phenyl‐1,3‐dihydrospiro[indene‐2,4′‐[1,3]oxazol]‐1‐yl acetate and its 5‐chloro‐ and bromoderivatives as products of interaction of N‐benzoylglycine (hippuric acid) with corresponding ortho‐formylbenzoic acids. The reaction carried out in acetic anhydride media in the presence of piperidine as catalyst. The novel spirocompounds were purified by column chromatography from multicomponent reaction mixtures. The composition of the spiro‐products was confirmed by C, H, N element analysis. The structure was established by IR, MS, ¹H‐ and ¹³C‐NMR analysis including COSY ¹H‐¹³C experiments.     

Synthesis of (3‐N‐substituted‐piperidin‐4‐ylidene)acetic Acid Ethyl Esters

A convenient preparation of skeletons 2A and 2B (cyclic γ,δ‐diamino‐α,β‐unsaturated esters) is reported by a three‐step synthetic route based on a sequence of NBS‐mediated one‐pot α‐bromination/Wittig olefination of piperidin‐4‐one 3 , nucleophilic addition with NaN₃, and followed by PPh₃‐promoted Staudinger reduction/substitution or CuI‐catalyzed Huisgen 1,3‐dipolar cycloaddition.     

Tandem Insertion–[1,3]‐Rearrangement: Highly Enantioselective Construction of α‐Aminoketones

An enantioselective synthesis of α‐aminoketone derivatives were readily available through a tandem insertion–[1,3] O‐to‐C rearrangement reaction. The rhodium salt and chiral N,N′‐dioxide‐indium(III) complex make up relay catalysis, which enables the O?H insertion of benzylic alcohols to N‐sulfonyl‐1,2,3‐triazoles, and asymmetric [1,3]‐rearrangement of amino enol ether intermediates, subsequently. Preliminary mechanistic studies suggested that the [1,3] O‐to‐C rearrangement step proceeded through an ion pair pathway.     

Synthesis and Triethylamine‐catalyzed Cyclization Reaction of 4‐Pentyne‐1,3‐dione System Having Various Substituents

4-Pentyne-1,3-dione system having various substituents was synthesized in two steps and the cyclization behavior of the obtained 1,3-dicarbonyl compounds was examined. γ-Pyrones and 2-alkylidene-2,3-dihydro-3-furanones were obtained by the triethylamine-catalyzed cyclization of the 4-pentyne-1,3-dione system having a diketone moiety. Furthermore, a phenol derivative was obtained in the case of 4-pentyne-1,3-dione system having an ester moiety. Thus, it was found that the kind of substituents in the 4-pentyne-1,3-dione system remarkably influenced the selectivity in the cyclization.     

Palladium‐catalyzed cyclization of β‐bromo‐α,β‐unsaturated ketones with arylhydrazines leading to 3‐substituted 1‐aryl‐1 H‐pyrazoles

β‐Bromo‐α,β‐unsaturated ketones are condensed with arylhydrazines to form hydrazones, which are in situ intramolecularly cyclized into 3‐substituted 1‐aryl‐1 H‐pyrazoles under a catalytic system of Pd(OAc)₂/1,3‐bis(diphenylhosphino)propane (dppp)/NaO^tBu. Copyright © 2012 John Wiley & Sons, Ltd.     

经由三丁基锡化氢、炔基砜和炔基溴的锡氢化-Stille串联反应“一锅”立体选择合成( Z)-2-砜基取代的1,3-烯炔

炔基砜和三丁基锡化氢在四(三苯基膦)钯催化下于苯中室温下进行锡氢化反应4 h,经溶剂转换成DMF后,再在CuI助催化剂存在下与炔基溴化物于室温进行Stille偶联反应,以良好产率且立体选择性地合成了( Z)-2-砜基取代的1,3-烯炔。该“一锅”合成法具有起始原料易得、反应条件温和、操作简便、钯催化剂利用率高和产率好等优势。     

Organocatalytic Enantioselective Synthesis of Tetrasubstituted α‐Amino Allenoates by Dearomative γ‐Addition of 2,3‐Disubstituted Indoles to β,γ‐Alkynyl‐α‐imino Esters

The first asymmetric synthesis of tetrasubstituted α‐amino allenoates by a chiral phosphoric acid catalyzed dearomative γ‐addition reaction of 2,3‐disubstituted indoles to β,γ‐alkynyl‐α‐imino esters is reported. This method provides access to a series of highly functionalized tetrasubstituted allenes featuring quaternary stereocenters in high yields, and with excellent regio‐, diastereo‐, and enantioselectivities under mild conditions without by‐product formation. Representative large‐scale reactions and diverse transformations of the products into various scaffolds with potential biological activities render are also disclosed. The mechanism of the reaction was elucidated by control reactions and DFT calculations.     

Regio‐ and Enantioselective Rhodium‐Catalyzed Addition of 1,3‐Diketones to Allenes: Construction of Asymmetric Tertiary and Quaternary All Carbon Centers

An unprecedented highly regio‐ and enantioselective rhodium‐catalyzed addition of 1,3‐diketones to terminal and 1,1‐disubstituted allenes furnishing asymmetric tertiary and quaternary all‐carbon centers is reported. By applying a Rh^I/phosphoramidite/TFA catalytic system under mild conditions, the desired chiral branched α‐allylated 1,3‐diketones could be obtained in good to excellent yields, with perfect regioselectivity and in high enantioselectivity. The reaction shows a broad functional‐group tolerance on both reaction partners highlighting its synthetic potential.     

Cycloaddition reactions of 1,3-diazabuta-1,3-dienes with alkynyl ketenes

The cycloaddition reactions of ‘all-carbon’ 1,3-diazabuta-1,3-dienes with a few conjugated and unconjugated alkynyl ketenes are described. The reactions provide some interesting azetidinones and dihydropyrimidinones bearing an alkynyl moiety. The regiochemistry of cycloadduct is related with the degree of conjugation of the alkynyl ketene. Moreover, two alternative approaches to ‘all-carbon’ 1,3-diazabuta-1,3-dienes are reported.     

Direct Conjugate Addition of Alkynes with α,β‐Unsaturated Carbonyl Compounds Catalyzed by NCN‐Pincer Ru Complexes

NCN‐pincer Ru‐complexes containing bis(oxazolinyl)phenyl ligands serve as suitable catalysts in the direct conjugate additions of α,β‐unsaturated carbonyl compounds, including ketones, esters, and amides, as well as vinylphosphonates, giving various β‐alkynyl carbonyl and phosphonate compounds. A bis(oxazolinyl)phenyl (phebox)–Ru complex also catalyzes the asymmetric conjugate addition of an alkyne with a β‐substituted, α,β‐unsaturated ketone to produce a chiral β‐alkynyl ketone.     

Synthesis of 3‐(ω‐Hydroxyalkoxy)isobenzofuran‐1(3H)‐ones by Trifluoroacetic Acid‐Mediated Lactonization of tert‐Butyl 2‐(1,3‐Dioxol‐2‐yl)‐ or 2‐(1,3‐Dioxan‐2‐yl)benzoates

An efficient two‐step method for the preparation of 3‐(2‐hydroxyethoxy)‐ or 3‐(3‐hydroxypropoxy)isobenzofuran‐1(3H)‐ones 3 has been developed. Thus, the reaction of 1‐(1,3‐dioxol‐2‐yl)‐ or 1‐(1,3‐dioxan‐2‐yl)‐2‐lithiobenzenes, generated in situ by the treatment of 1‐bromo‐2‐(1,3‐dioxol‐2‐yl)‐ or 1‐bromo‐2‐(1,3‐dioxan‐2‐yl)benzenes 1 with BuLi in THF at ?78°, with (Boc)₂O afforded tert‐butyl 2‐(1,3‐dioxol‐2‐yl)‐ or 2‐(1,3‐dioxan‐2‐yl)benzoates 2 , which can subsequently undergo facile lactonization on treatment with CF₃COOH (TFA) in CH₂Cl₂ at 0° to give the desired products in reasonable yields.     

Photolysis of α,β‐Epoxyketones: A Green Synthesis of β‐Hydroxyenones through Tandem H‐Abstraction,Ring Cleavage and Isomerisation

The photochemical behavior of various substituted epoxycarbonyl compounds consisting of more than one possible photo‐labile site (i.e. δ‐hydrogen, β‐hydrogen and epoxide ring) has been investigated. These compounds on photo‐irradiation produced the β‐hydroxyenones in an eco‐friendly green approach. Mechanistically, these photo‐transformations have been envisaged to occur via an intramolecular β‐hydrogen abstraction by the carbonyl group of benzoyl moiety to generate the 1,3‐biradical followed by epoxide ring opening that isomerizes into the photoproducts. The photolysis of the probed epoxy ketones didn’t furnish any photoproduct through δ‐hydrogen abstraction, whatsoever. This exclusive preference for β‐H abstraction over δ‐H abstraction by carbonyl group has been vindicated by the MM2 energy mini‐ mized program for the investigated photochemical substrates. The structures of these photoproducts were established from the analysis of their spectral parameters (IR, ¹H/¹³C NMR and Mass) and single crystal X‐ray crystallography data.     

Nitriles in Heterocyclic Synthesis: Reactivity of 2‐(Benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one towards α,β‐Unsaturated Nitriles

The reaction of 2‐(benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one 1 with α,β‐cinnamonitrile derivatives 2a‐n have been reported.