Selectivity variation in hydrolysis of phenyl acetates by simple modifications of β-cyclodextrin.

By reaction of β-cyclodextrin 6-monotosylate with alkyl mercaptans, 6-deoxy-6-alkylthio-β-cyclodextrins, $\text{2}$, $\text{3}$, and $\text{4}$, were prepared. Studies of the hydrolyses of $\text{m}$- and $\text{p}$-substituted phenyl acetates showed that the well-known meta-selectivity effect occurred with $\text{2}$, while none was observed with $\text{4}$. This variation in selectivity was due to a change in the catalytic rate constant caused by the substituent on β-cyclodextrin.     

5,12-dihydro-6,11-didehydronaphthacene,A derivative of 1,4-didehydronaphthalene

Treatment of the di-lithium derivative of 1,2-diethynyl-benzene ($\text{1}$) with $\text{o}$-xylene-α,α′-diol di-$\text{p}$-toluenesulphonate ($\text{2}$) in tetrahydrofuran led to 5,12-dihydronapthacene ($\text{5}$) as the only identifiable product. This reaction presumably involves 5,12-dihydro-6,11-didehydronaphthacene ($\text{4}$) as an intermediate, and this was confirmed by the formation of 5,12-dihydro-6,11-dideuterio-naphthacene when the reaction was carried out in tetrahydrofuran-$\text{d}$₈.     

Studies on the reaction of 1,2-dicarbonyl compounds with dimethyl 3-ketoglutarate. Steric and electronic effects

The steric and electronic influences of substituents attached to the 1,2-dicarbonyl system on the success of the reaction of 1,2- diketones with dimethyl 3-ketoglutarate $\text{2}$ have been examined. It is clear from the reaction of $\text{2}$ with benzil, thienil, furil, and phenanthrenequinone $\text{5}$, respectively, coupled with ¹³C NMR spectroscopy of the reaction intermediates, that steric effects play a major role in the overall success of the reaction to provide $\text{4}$. This is analogous to the situation observed earlier with 1,2-diketones, R-CO-CO-R, where R represented an aliptiatic or alicyclic group.     

Synthesis of 4a-, 4e-phenyladamantanones and 2,4-o-benzenoadamantane by π-route

The acid catalysed reaction of 4-oxa-homoadamantan-5-one ($\text{1}$) with benzene yielded a mixture of 4^a-phenyladamantan-2-one ($\text{7}$), the equatorial isomer' ($\text{8}$) and 2-phenyl-2,4-o- benzenoadamantane ($\text{9}$) A plausible reaction pathway for the occurrence of $\text{9}$. is put forward. The structure of $\text{9}$, was deduced from spectroscopic data and reaction of the proposed intermediate 2,4^a-diphenyladamantan-2-ol ($\text{11}$) with acid. 2,4-o-Ben-zenoadamantane ($\text{16}$) is prepared likewise.     

Fluoroimines from the reaction of fluoroamino acids or fluoroketo acids with the aldehyde or amine form of vitamin B6: Part III. Influence of fluorine on the formation and the reactivity of fluoroimines derived from β-fluoroaspartates or β-fluorooxaloacetate

The introduction of fluorine at the β-position in aspartate and in oxaloacetate, the typical amino acid-keto acid couple in transamination, induces large effects in their reaction with respectively pyridoxal 5′-phosphate (PLP) ($\text{1}$) and pyridoxamine 5′-phosphate (PMP) ($\text{4}$). The formation of imine intermediates through reaction of $\text{1}$ with $\text{erythro}$ or $\text{threo}$-β-fluoroaspartate ($\text{2e}$ and $\text{2t}$) and through reaction of $\text{4}$ with β-fluorooxaloacetate $\text{5}$ is highly favored in comparison with that of non-fluoro compounds. The stereoisomers of the imines are unambiguously determined using a reduction reaction. The evolution of these intermediates shows that no transaminatlon is observed and that a dehydrofluorination occurs suggesting that the β-fluoro moiety in the intermediate turns into a good leaving group, changing the model reaction of transamination on α carbon through the aldimine-ketimine tautomerization to an elimination on β carbon.     

Acid-catalyzed cyclizations of n-vinyl-α-sulfinylacetamides A novel synthetic approach to erythrinane

Under the Pummerer reaction conditions, N-(1-cyclohexenyl)-N-methyl-α-(methylsulfinyl)acetamide ($\text{7a}$) cyclized in a 5-endo trigonal fashion through the intermediary cation ($\text{8}$) to give the tetrahydro-4H-oxindole ($\text{10}$). The reaction was successively applied to a novel synthesis of erythrinane skeleton.     

1,2-dimagnesium derivatives of cyclopropane

cis-1,2-Dibromomagnesiocyclopropane (cis-$\text{4}$) was isolated from the reaction of both trans- and cis-1,2-dibromocyclopropane ($\text{1}$) with magnesium. The corresponding dialkylmagnesium species ($\text{7}$), an oligomer of 2-magnesabicyclobutane, was obtained from cis-$\text{4}$ by precipitation in THF; it forms a soluble complex 8 with HgBr₂.     

Dedoublement et configuration absolue de la methyl-3 δ3(3a)-hydrindenone-4.etude de l'isomerisation en methyl-3 δsu3a(7a)-hydrindenone-4.

During the hydrogenation of the Δ^3(3a)-4-hydrindenones $\text{1}$ or $\text{3}$ on Pd or Ni, we observe a shift of the double bond to Δ^3a(7a)-4-hydrindenones $\text{2}$ and $\text{4}$. The absolute configuration established for ketones $\text{1}$ and $\text{2}$ shows that the reaction is a suprafacial process. By deuteriation experiments, we observe that the reaction is irreversible and occurs with a molecular hydrogen exchange.     

Cycloaddition of diphenylnitrilimine to coumarins. The synthesis of 3a,9b-dihydro-4-oxo-1H-benzopyrano [4 ,3-c]pyrazole derivatives

The cycloaddition of diphenylnitrilimine to a series of coumarins occurs with the same regioselectivity in all cases, regardless the nature of the substituent present, to yield the corresponding 3a,9b-dihydro-4-oxo-lH-benzopyrano [4,3-c]pyrazoles $\text{4}$a–f. Dehydrogenation of $\text{4a}$ yields 4-oxo-1H-benzopyrano [4,3-c]-pyrazole $\text{6}$. In ethanolic sodium ethoxide solution, the reaction between coumarin and diphenylnitrilimine precursor, namely N-phenylbenzohydrazidoyl chloride $\text{1}$, affords no cycloadducts, but yields o-(β-ethoxycarbonylvinyl)phenyl N-phenylbenzohydrazidate $\text{10}$. The regiochemistry of the cycloadducts $\text{4}$a–f and the reaction sequence leading to $\text{10}$ are outlined. The structures of the products have been established by spectroscopic methods and independent syntheses wherever possible.     

α-Phenylselenenylation d'aldehydes - synthese simple d'α-cetoaldehydes a fonction cetone protegee

Morpholinophenylselenenamide $\text{2}$ add to β-phenylselenoenamines $\text{1a}$ and yield β,β-bis(phenylseleno) enamines $\text{4}$. These compound undergo hydrolysis to form bis(phenylseleno) ethanal $\text{5a}$. Also, $\text{2}$ react with enolic aldehydes to give α-phenylselenoaldehydes $\text{3}$. This reaction allow a “one step” synthesis of cetoselenoacetals $\text{5}$ of α-cetoaldehydes with good yields.     

The facile (<−50°C) formation of cis-bicyclo[6.1.0]nona-2,4,6-trienes from cyclonona-1,3,5,7-tetraenes: A symmetry - forbidden reaction

The formation of the $\text{cis}$-bicyclo [6.1.0] nona-2,4,6-trienes $\text{4a}$-$\text{c}$ is not due to the sequence $\text{1}$ → $\text{2}$ → $\text{4}$, which would involve the symmetry-forbidden reaction $\text{2}$ → $\text{4}$ even at ?50°C. Rather, reaction of RX at C^4–7 of $\text{5}$, which is formed together with $\text{1}$, leads (probably via $\text{6a}$-$\text{c}$ and $\text{7a}$-$\text{c}$ to $\text{4a}$-$\text{c}$.     

Seco-aldehydes from didroval tratum

Primary iodides, obtained from didrovaltratum ($\text{1}$) on treatment with hydriodic acid in methanol, are transformed into seco-aldehydes $\text{5}$ and $\text{6}$ in a fragmentation reaction. Both aldehydes very similar to secologanine yield various condensation products with tryptamine under Pictet-Spengler conditions. The relative and absolute configuration of the crucial intermediate $\text{4}$ was secured by X-ray structure analysis.     

Photochemistry of 4-pyrimidinones in aqueous solution. Isolation of reversible photohydrates

Both the irradiation of 4-pyrimidinones ($\text{la-c}$) and the reaction of the isolated Dewar 4-pyrimidinones ($\text{2a-c}$) in aqueous solution gave the corresponding photohydrates ($\text{3a-c}$) which reverted spontaneously to the starting $\text{la-c}$ in the dark reaction. The photohydrates were isolated in crystalline form and their physical properties were determined.     

Synthesis and thermal rearrangement of a potential butalene-anthracene adduct

The synthesis of propellane $\text{4}$, a formal Diels-Alder adduct of 1,4-dehydrobenzene and anthracene, is reported. This material does not undergo a retro-Diels Alder reaction on pyrolysis, but instead rearranges to benzofluoranthene $\text{5}$.     

Inept-29Si NMR study of a TiCl4-mediated reaction of an enol silyl ether

Condensation of 1,3-bis(trimethylsiloxy)-1-methoxybutadiene ($\text{1}$) and 2-phenyl-2,2-dimethoxyethanal ($\text{2}$) under TiCl₄ condition gave the γ-hydroxycyclopentenone product $\text{3}$. The reaction was followed by INEPT²⁹Si NMR. Implication to the mechanism of the reaction was discussed.     

On the reaction of orsellinic acid carbanion with pyrylium salts

From the reaction of methyldimethyl orsellinate anion $\text{1}$ with the pyrylium salt $\text{2}$ the isocoumarin $\text{5}$ was isolated in addition to the pyrones $\text{3}$ and $\text{4}$. Reaction intermediates could be trapped as pyridines $\text{6}$ and $\text{7}$.     

Monitored aminolysis of 3-acylthiazolidine-2-thione : A new convenient synthesis of amide

3-Acylthiazolidine-2-thiones ($\text{1}$) were easily prepared and they were treated with several amines in dichloromethane to give amides $\text{4}$ in very high yields within a short time. Aminoalcohols and aminophenols were selectively converted into acylaminoalcohols and acylaminophenols, respectively, by this reaction. One can monitor the reaction by disappearance of the yellow color of the starting material $\text{1}$. Some amide alkaloids ($\text{1}$$\text{5}$–$\text{1}$$\text{8}$) have effectively been synthesized.     

Synthesis of trans-1,2-diphenyl-3,4-bis[4-(2,6-diphenyl-4H- pyranylidenyl)]cyclobutane: correction and structure proof

The reaction of phenyl lithium acetylide ($\text{2}$) with 2,6-diphenylpyrylium perchlorate ($\text{1}$) is solvent dependent. With diethyl ether as solvent, the isolated product differed from that previously reported and is reassingned as 2,6-diphenyl-4-phenylacetylenyl-4$\text{H}$-pyran ($\text{5}$). On the other hand, in THF the title compound ($\text{6}$) was obtained; its structure confirmed by single-crystal x-ray crystallography.     

Interactions of singlet oxygen with 2,5-dimethyl-2,4-hexadiene in polar ano non-polar solvents evidence for a vinylog ene-reaction

2,5-Dimethyl-2,4-hexadiene ($\text{1}$)was studied as a singlet oxygen acceptor in various solvents. $\text{1}$undergoes concomitantly the three well-known modes of singlet oxygen reactions: (1) the ene-reaction to give the allylic hydroperoxide $\text{3}$, (2) the (4+2)-cycloaddition to give the endoperoxide $\text{4}$, and (3) the (2+2)-cycloaddition to give the dioxetane $\text{2}$. Beyond that (and in contrast to simple olefins), there are (4) “physical” quenching and (5) a “vinylog ene-reaction” to give the twofold-unsaturated hydroperoxide $\text{5}$. The latter reaction represents a novel mode of singlet oxygen interaction with a substituted 1,3-diene. - Kinetic analysis shows that “physical” quenching, endoperoxide and vinylog ene-product formations proceed with solvent-inde pendent rates; the rates of dioxetane and ene-product formations, however, are solvent-dependent. - A mechanism (Scheme 3) is proposed, according to which endoperoxide formation is due to a concerted singlet oxygen reaction with the s-cis-conformational isomer $\text{1b}$; with the s-trans-isomer $\text{1a}$, “physical” quenching and the vinylog ene-reaction proceed via a non-polar singlet diradical intermediate, whereas the ene-product formation occurs via a per epoxide-like transition state. In aprotic solvents, the dioxetane is mainly formed via a “tight-geometry intermediate”, in methanolic solution via a solvent-stabilized zwitterion; the latter is also responsible for the formation of the methanol-addition product $\text{6}$.     

Chemistry of 4-membered cyclic nitrones (2, 3-dihydroazete 1-oxides); a novel one-step synthesis of N-acetoxy β-latams

2,3-dihydroazete 1-oxide $\text{1}$ reacts at room temperature with base, acid and lead tetraacetate to give the 5-hydroxyisoxazolidines $\text{4a}$ and $\text{4b}$, the 6H-1,2-oxazin-6-one $\text{7}$ and the N-acetoxy β-lactam $\text{8}$, respectively; the reaction with lead tetraacetate represents a simple one-step conversion of a 4-membered cyclic nitrone into a β-lactam.