Good Combined Yield Research Articles

Decarboxylation of Paraconic Acids by a Silver(I) Nitrate/Persulfate Combination: An Entry to β-Nitro- and β-Hydroxy γ-Butyrolactones

AbstractDecarboxylative transformations of paraconic acids, a class of γ-butyrolactones containing a carboxylic acid group at the β-position as their characteristic functionality, by using a combination of AgNO3/K2S2O8 were investigated. The dual function of AgNO3 as an initiator of the decarboxylation process and as a source of nitrogen dioxide radicals that react with aliphatic carboxylic substrates is reported for the first time. Starting from paraconic acids, β-nitro- and β-hydroxy γ-butyrolactones were obtained in good combined yields (41–85%) with moderate selectivity in a one-pot operation. The reactions were completed within an acceptable reaction time (two hours) under mild conditions that were tolerated by the γ-butyrolactone core. This study provides a direct and site-specific entry to β-nitro- and β-hydroxy γ-butyrolactones, which are important precursors in organic transformations.

Stereoselective deconjugation of macrocyclic α,β-unsaturated esters by sequential amidation and olefin transposition: application to enantioselective phase-transfer catalysis.

The stereoselective synthesis of chiral macrocycles bearing two aliphatic amide functional groups is reported. After the amidation mediated by TBD, a guanidine derivative, the olefin transposition step is performed with a slight excess of t-BuOK. The products are afforded in moderate to good combined yields (up to 59%) and with an excellent syn diastereoselectivity (dr > 49 : 1). Introducing enantiopure α-branched substituents was possible and it resulted in mixtures of diastereomers, which could be tested as phase-transfer catalysts using the formation of a phenylalanine analog as a test reaction (up to 43% ee). A clear matched-mismatched situation was observed in the two diastereomeric series.

Face‐ and Regioselectivity in Electrophilic Phenylsulfenylation of 7‐tert‐Butoxybicyclo[2.2.1]hepta‐2,5‐dienes

ABSTRACTElectrophilic phenylsulfenylation of syn‐7‐tert‐butoxy‐2‐phenylsulfonyl‐ bicyclo[2.2.1] hepta‐2,5‐diene with phenylsulfenyl chloride yielded a mixture of three simple adducts, two of which were derived by the endo face attack of the phenylsulfenyl cation. In the analogous reaction with the anti derivative, only one adduct with the exo phenylsulfanyl group at the nearer carbon was obtained. This product was derived by the attack of the phenylsulfenyl cation from the exo face followed by the endo attack of a chloride anion at the carbon opposite to the phenylsulfonyl group. The similar reaction of 7‐tert‐butoxybicyclo[2.2.1]hepta‐2,5‐diene itself underwent no Wager–Meerwein‐type rearrangement or transannular reaction, and simple adducts were formed in good combined yield. The combined yield of the products reacted at the syn double bond was ca. 80%.

A novel MgI2 mediated unusual dimerization–spirocyclopropanation of bromo isomerised Morita–Baylis–Hillman adduct of isatin: a facile synthesis of 3-spirocyclopropane-2-oxindole derivatives

A novel magnesium iodide mediated unusual dimerization–spirocyclopropanation of bromo isomerised Morita–Baylis–Hillman adducts of isatin afforded highly functionalized 3-spirocyclopropane-2-oxindole derivatives as regioisomers in good combined yield. It has been observed that the regioselectivity is dependent on the nature of electron withdrawing group at the activated position. A plausible mechanism involving organomagnesium reagent has been proposed.

Selective and Random Syntheses of [n]Cycloparaphenylenes (n = 8–13) and Size Dependence of Their Electronic Properties

[n]Cycloparaphenylenes (n = 8-13, CPPs) were synthesized, and their physical properties were systematically investigated. [8] and [12]CPPs were selectively prepared from the reaction of 4,4'-bis(trimethylstannyl)biphenyl and 4,4''-bis(trimethylstannyl)terphenyl, respectively, with Pt(cod)Cl(2) (cod = 1,5-cyclooctadiene) through square-shaped tetranuclear platinum intermediates. A mixture of [8]-[13]CPPs was prepared in good combined yields by mixing biphenyl and terphenyl precursors with platinum sources. Products were easily separated and purified by using gel permeation chromatography. In (1)H NMR spectra, the proton of the CPPs shifts to a lower field as n increased due to an anisotropic effect from the nearby PP moieties. Although the UV-vis spectra were rather insensitive to the size of the CPPs, the fluorescence spectra changed significantly in relation to their size. A larger Stokes shift was observed for the smaller CPPs. Redox properties of the CPPs were measured for the first time by using cyclic voltammetry, and the smaller CPPs had lower oxidation potentials. The results are consistent with the HOMO energies of CPPs, of which the smaller CPPs had higher energies.

ChemInform Abstract: Phosphorus-Nitrogen-Selenium Ring Systems.

Abstract Diphosphadiselenatetrazocines, 1,5-R4P2Se2(R = Me, Et, Ph) and 1,3-R4P2N4Se2 (R = Me, Et), have been prepared in good combined yields from the cyclocondensation of R2PN2(SiMe3) with ‘SeCl3’. The compound 1,5-Ph4P2N4Se2 dissociates into Ph PN2Se radicals identified by ESR spectroscopy. Metal complexes (Ph3P2) (M = Pt, Pd) have been prepared from the reaction of 1,5-Ph4P2N4Se2 with (Ph3P)2PtC2H4 and (Ph3),Pd, respectively. The Se,Se'-dialkyl denvatives 1,5-Ph4P2N4Se2R2 undergo isomerization to produce 1,3-Ph4P2N4 2 in the solid-state (R = Me, Et) or, more rapidly, in solution (R = Me, Et, Ph).

Synthesis of β‐Methoxyacrylate Natural Products Based on Box‐PdII‐Catalyzed Intermolecular Methoxycarbonylation of Alkynoles

Bis(oxazoline)-palladium(II) catalyzed carbonylation of homopropargyl alcohols afforded acyclic methoxyacrylate 2 and 6-membered lactone 3a-k in good combined yield. In the case of propargyl alcohols, 5-membered lactones 3p, 3q, 16 were obtained in moderate yields. The one-pot synthesis of kawa lactones 3a, 3r, 3s and formal synthesis of dihydroxycystothiazole A and dihydroxycystothiazole C are presented. To elucidate the stereochemistry of (+)-annularin G and (-)-annularin H, the first asymmetric syntheses of these natural products were achieved.

A new approach to benzofuran synthesis: Lewis acid mediated cycloaddition of benzoquinones with stilbene oxides

We report a BF 3-mediated novel dehydrative cycloaddition reaction of benzoquinones with stilbene oxides to afford 2,3-diaryl-5-hydroxybenzofurans and 2,3-diaryl-5-hydroxydihydrobenzofurans in good combined yields. No change in the products or the yield is observed when using diphenylacetaldehyde and cis-stilbene oxide instead of trans-stilbene oxides. When stilbene oxide is reacted with hydroquinone instead of the corresponding benzoquinone under the same conditions, dihydrobenzofuran is isolated in high yield. On the basis of these results, we propose the following possible reaction mechanism: stilbene oxide is converted to a phenonium ion (the key intermediate), which undergoes nucleophilic attack by benzoquinone or the simultaneously generated hydroquinone and subsequent dehydrative intramolecular cyclization to afford benzofuran or dihydrobenzofuran, respectively.

Photoacylations of 2-substituted 1,4-naphthoquinones: a concise access to biologically active quinonoid compounds

Photochemical acylations of 2-substituted-1,4-naphthoquinones with various aldehydes furnished acylated hydroquinones and acylated quinones in moderate to good combined yields. All reactions are easily performed and open a rapid access to biologically active compounds. For the 2-methyl-1,4-naphthoquinone/butyraldehyde pair, a novel tri-keto compound has been additionally isolated.

The photochemistry of 1-cyclohexenyl-2,4,6-trimethylphenyl-methanone (1-mesitoyl-cyclohexene)

The photochemistry (direct irradiation in solution, λ>300 nm ) of the title compound ( 8) has been investigated. Whereas, in contrast to the methyl-free analog of 8, only undefined material of higher molecular weight was obtained upon irradiation without additives in acetonitrile and toluene, this situation changed dramatically in the presence of co-reactants. Thus, in ethyl vinyl ether, [4+2] adducts 11a and 11b were obtained in good combined yield. In acetonitrile, in the presence of acid which catalyses a skeletal rearrangement, the hexahydrofluorenone 14 was the main product. The results point to the intermediacy of the trans-cyclohexene isomer of 8, viz. 9, and to the 2-oxyallyl 10 as consecutive intermediates, in analogy to the methyl-free system. The molecular structures of some unprecedented minor by-products such as 15a– c even more clearly reveal their origin from 10. Photoreactions of 8 in the presence of either water or phenol as co-reactants proceeded less cleanly but did give defined products such as 16– 18 in moderate yields.

An allyltitanium derived from acrolein 1,2-dicyclohexylethylene acetal and (eta(2)-propene)Ti(O-i-Pr)(2) as a chiral propionaldehyde homoenolate equivalent that reacts with imines with excellent stereoselectivity. An efficient and practical access to optically active gamma-amino carbonyl compounds.

A chiral allyltitanium compound 2, prepared in situ by the reaction of optically active acrolein 1,2-dicyclohexylethylene acetal (3) with (eta(2)-propene)Ti(O-i-Pr)(2) (1), reacts with a variety of acyclic and cyclic imines 4 in a regiospecific way to afford alpha-addition products 5 as a mixture of the E- and Z-isomers in good combined yield, where the former is predominant in a ratio of 92:8 to >95:5. The mixture of (E)- and (Z)-5 and pure (E)-5 which could be isolated in several cases were respectively converted to the corresponding beta-amino ester 6 to confirm the absolute configuration and enantiomeric purity. The ee of the newly formed asymmetric center of 5 is more than 78% for the mixture of (E)- and (Z)-5 and more than 96% for pure (E)-5. By taking advantage of the versatility of the vinyl ether moiety in 5, optically active gamma-amino aldehydes 8, gamma-amino aldehyde acetals 7 and 10, gamma-amino acids 9, beta-amino esters 6, and pyrrolidinoisoquinolines 12 were readily prepared. In the reaction of 2 with optically active alpha-silyloxyimine 4n, remarkable double stereodifferentiation was observed; thus, the reaction of 2 derived from (S,S)- or (R,R)-3 provided syn- and anti-5n in a ratio of 55:45 or 0:100, respectively. Meanwhile, the stereochemistry of the product in the reaction of 2 with beta-silyloxyimine 4o was controlled mainly by 2. Thus, the reaction of beta-silyloxyimine 14 with 2 derived from 1 and (R,R)-3 afforded gamma-silyloxyimine 15 with 92% diastereoselectivity, from which 4-amino-6-hydroxypentadecanal dimethyl acetal (13), a key intermediate for the synthesis of batzelladine D, was synthesized.

Reductive Cyclization of (3-) and (4-Oxoalkyl)-9,10-anthraquinones to the cyclopenta[a]anthraquinone and naphthacene-5,12-dione systems

Reductive cyclization of the 1-hydroxy-3-(3-oxoalkyl)-9,10-anthraquinones 2, 9 and 10 yields the angularly condensed cyclopenta[a]anthraquinones 3, 21 and 22a under neutral conditions (DMF/Na2S2O4). By contrast, the linear cyclopenta[b]anthraquinone 23 is isolated from 10 applying the usual alkaline Marschalk conditions (aqueous methanol, NaOH, Na2S2O4). The linearly condensed 5,12-naphthacenequinones 24–28 of different degree of saturation are obtained in good combined yield from the corresponding 1-hydroxy-3-(4-oxoalkyl)-9,10-anthraquinones 19 and 20 under the conditions of the Marschalk reaction.

Inter- and Intramolecular Diels-Alder Cycloaddition of Enantiopure 4,5-O, C-Functionalized Cyclohex-2-Enone and Its Derivatives Prepared from D-Glucose1

The Lewis acid catalyzed reaction of a D-glucose derived functionalized cyclohex-2-enone 1 with furan provided the 1,4-conjugate adducts 3 and 4. On the other hand, thermal intermolecular Diels-Alder cycloaddition of 1 with 1,3-cyclohexadiene provided two endo-cycloadducts 5 and 6 in a good combined yield. The intramolecular cycloaddition of sorbic acid ester 20 of the allylic alcohol 19, prepared from 1, proceeded under thermal conditions to give a mixture of highly functionalized decalin derivatives 21-23, whose stereostructures were determined by chemical modification. 1. Presented at the XVIIIth International Carbohydrate Symposium, Milan, Italy, July 21-26, 1996.

Aromatic Nitration under Neutral Conditions Using Nitrogen Dioxide and Ozone as the Nitrating Agent. Application to Aromatic Acetals and Acylal

Abstract Cyclic acetals derived from aromatic carbonyl compounds can be nitrated smoothly with nitrogen dioxide in ice-cooled dichloromethane or acetonitrile in the presence of ozone and magnesium oxide to give ortho- and para-nitro derivatives as the major product in good combined yields, the acetal ring as a protective group remaining almost intact. An acylal derived from benzaldehyde similarly undergoes nitration on the aromatic ring to give an isomeric mixture of three nitro compounds, in which the ortho and meta isomers predominate, while aromatic orthoesters are rapidly decomposed to give simply the parent esters. Ring nitration under neutral conditions has been interpreted in terms of a nonclassical mechanism, in which nitrogen trioxide is involved as the initial electrophile.

Cycloadditions of methano[11]annulenones with dichloro- and chloro-ketenes. Preparation of 2H-methanocycloundeca[b]furan-2-one ring systems

Cycloaddition of dichloroketene with 3,8-methano[11]annulenone 5 proceeded smoothly to give 3-Chloro-2H-4,9-methano- and 3-Chloro-2H-6,11-methano-cycloundeca[b]furan-2-ones 4a and 7a in good combined yield, while that with 4,9-methano[11]annulenone 6, gave 3-Chloro-2H-5,10-methanocycloundeca[b]furan-2-one 11a in modest yield. Reductive elimination of the 3-chlorosubstituent of 4a, 7a and 11a was successfully accomplished to give the corresponding parent 2H-methanocycloundeca[b]furan-2-ones 4b, 7b and 11b, respectively. In a similar reaction using chloroketene, compound 5 gave unsubstituted-, 3-chloroacetyl- and 3-(1-chloroacetoxy-2-chloro)vinyl-2H-4, 9-methanocycloundeca[b]furan-2-ones 4b, 19 and 20 in good combined yield, while with 6, only 3-chloroacetyl-2H-5,10-methanocycloundeca[b]furan-2-one 21 was obtained in modest yield. The reactivity and/or regioselectivity of the Cycloadditions were rationalized on the basis of AM1 calculations. An X-ray crystallographic determination of compound 4a was also carried out.

Ozone-mediated reaction of aromatic acetals and acylal with nitrogen dioxide: a novel methodology for the nuclear nitration of acid-sensitive aromatic compounds under neutral conditions

Cyclic acetals 1c–e and 1g can be nitrated smoothly with nitrogen dioxide in ice-cooled dichloromethane in the presence of ozone and magnesium oxide to give mainly ortho- and para- nitro derivatives in good combined yields, the acetal protective group remaining almost intact; acylal 6 is similarly nitrated on the aromatic ring to give a mixture of isomeric nitro derivatives 7, in which the ortho and meta isomers predominate.

Phosphorus-Nitrogen-Selenium Ring Systems

Abstract Diphosphadiselenatetrazocines, 1,5-R4P2Se2(R = Me, Et, Ph) and 1,3-R4P2N4Se2 (R = Me, Et), have been prepared in good combined yields from the cyclocondensation of R2PN2(SiMe3) with ‘SeCl3’. The compound 1,5-Ph4P2N4Se2 dissociates into Ph PN2Se radicals identified by ESR spectroscopy. Metal complexes (Ph3P2) (M = Pt, Pd) have been prepared from the reaction of 1,5-Ph4P2N4Se2 with (Ph3P)2PtC2H4 and (Ph3),Pd, respectively. The Se,Se'-dialkyl denvatives 1,5-Ph4P2N4Se2R2 undergo isomerization to produce 1,3-Ph4P2N4 2 in the solid-state (R = Me, Et) or, more rapidly, in solution (R = Me, Et, Ph).

The Synthesis and Properties of Three Isomers of 1-Troponyl-1H-1,2-diazepine

Abstract The substitution reaction of 2-halotropones or 2-tosyloxytropone with tricarbonyl(4-7-η-1H-1,2-diazepine)iron afforded three isomers of tricarbonyl(4-7-η-1-troponyl-1H-1,2-diazepine)iron in good combined yield: three complexes were decomplexed to novel three isomers of 1-troponyl-1H-1,2-diazepine.

Photolysis of 7-Oxanorbornadienes Condensed with Tropone. A Facile Formation of 6-Hydroxyazulenes

Abstract Irradiation of 12-oxatricyclo[7.2.1.02,8]dodeca-2(8),3,6,10-tetraen-5-ones having one or two bridge-head alkyl substituents in methanol with high pressure Hg lamp gave 6-hydroxy- or 1-alkyl-6-hydroxyazulenes together with 3-acyl- or 1-alkyl-3-acylazulenes as by-products in good combined yields.

ChemInform Abstract: NONACARBONYLDIIRON OR PENTACARBONYLIRON INDUCED DECOMPOSITION OF ORGANIC AZIDES AND AN AZIRINE. NOVEL REDUCTION AND CARBONYL INSERTION OF THE COMPLEXED NITRENE INTERMEDIATE IN PROTIC SOLVENTS

AbstractDie thermischen Reaktionen von Nonacarbonyldieisen und die photochemischen Reaktionen von Fe‐pentacarbonyl mit den Aziden (I) und (V) und dem Azirin (VIII) in protischen Medien werden untersucht.