Ozonolyse d'olefines perfluorees

We have obtained unusually stable secondaxy ozonides ($\text{2a-c}$) by heating neat perfluoroalkenes ($\text{1a-c}$) with ozone.     

Enamine chemistry—XXIII: The [4+2] cycloaddition reactions between enaminothiones and electrophilic olefins and acetylenes

The enamino-thione, 1c, reacts with acrylonitrile and 2-chloroacrylonitrile at room temperature to give 3,4-dihydro-4-(1-pyrrolidinyl)-2$\text{H}$-thiopyrans, 4 and 5, respectively. The reaction between 1-aryl-3-(1-pyrrolidinyl) (piperidino)-apropene-1-thiones, 1a-c (1d-f), and dimethyl acetylenedicarboxylate gives 4-(1-pyrrolidiny)(piperidino)-4$\text{H}$-thiopyrans, 6a-c (6d-f). Compounds 1a-c (1d-f) and ethyl propiolate produce 2-(1-pyrrolidinyl) (piperidino)-2$\text{H}$-thiopyrans, 8a-c (8d-f), and a new type of rearrangement is observed. The 2$\text{D}$-thiopyran, 9, is formed from 1b and ethyl 3$\text{D}$-propiolate, which elucidates the mechanism. ¹H and ¹³C NMR data of 6 and 7 are discussed.     

Regioselective Friedel-Crafts acetylation of 5-hydroxyindole derivatives: synthesis of 4H-pyranoindol-4-one derivatives

The Friedel-Crafts acetylation of 5-hydroxyindole derivativesla-c regioselectively produced 6-acetyl-5-hydroxy-indole derivatives2a-c which were condensed with cinnamic acid using POC1₃ and dry pyridine to afford 5-cinnamoyloxy-6-acetyl-indoles3a-c. These upon Baker-Venkataraman transformation furnished 6-cinnamoylacetyl-5-hydroxyindoles4a-c which were cyclised separately with AcOH/HCl and Ac₂O/AcONa to 4H-pyrano-(2,3-f)indol-4-one derivatives5a-c and6a-c respectively.     

6-alkyl- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones in the transformations of pyrimidines. Regiospecific 1-N-acylation of pyrimidines.

Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1-$\text{N}$-acylated-pyrimidine derivatives 3($\text{a}$-$\text{f}$) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1-$\text{N}$-acyl-protected-isouridine analogues (8a and 8b).     

A Useful Synthesis of 2-Methyl-2,3-dihydrofuro [2,3-b] Quinolines

A convenient, general synthesis of 2-methyl-2,3-dihydrofuro [2,3-b] quinolines is described from o-nitrobenzaldehydes. The benzaldehydes (la-c) on reaction with phosphorane 2 provide (E)-ethyl-α-allylcinnamates (3a-c) in high yields. These esters 3a-c on reduction followed by acid catalysed cyclisation give 2,3-dihydrofuro [2,3-b] quinolines (5a-c).     

Reaction of acylaminocyanoesters with 2,4-bis (4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide leading to substituted aminothiazoles. Crysta

2-Acylamino-2-cyanoacetic acid ethyl esters $\text{2a-c}$ react with 2,4-bis (4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane 2,4-disulfide $\text{1}$ in refluxing benzene with formation of 2-alkyl(aryl)-5-aminothiazole-4-carboxylic acid ethyl esters $\text{3a-c}$. Structure $\text{3}$ was established by spectroscopic means and an X ray crystallographic investigation of $\text{3a}$. X-Ray analysis revealed that the thiazole ring, exocyclic nitrogen and carbonyl group forming a hydrogen-bonded cycle are nearly coplanar. A resonance interaction is manifested by distinctly shortened /1.447 (3)/ C_(carbonyl)-C_(thiazole) distance.     

Regioselectivity in reactions of alkynylmetal complexes with pyrimidinones

Regioselectivity is observed in $\text{1}\text{1}$-adduct formation between phenylethynyltriisopropoxytitanium and 2(1/H)-pyrimidinones; the new carbon-carbon bond is formed at C(4). In contrast the 3,4- and 3,6-dihydro products are formed together from the corresponding magnesium and lithium reagents, but from the magnesium compound the major product is the 3,6-dihydro isomer. Ethynylmagnesium bromide gives equimolar amounts of the 3,4- and 3,6-dihydro isomers. Dehydrogenation of the products gives the alkynylated aromatic heterocycles.     

A new furoxan derivative and its precursors formed by the reaction of sorbic acid with sodium nitrite

A new furoxan derivative ($\text{3}$) and its precursors ($\text{4a}$ and $\text{4b}$) were isolated from the reaction mixture of sorbic acid with sodium nitrite, and their structures were determined by spectroscopic and X-ray crystallographic analysis.     

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.     

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.     

Acetylsanadaol,a diterpene having a novel skeleton,from the brown alga, Pachydictyon Coriaceum

Structures of new diterpenoids, sanadol ($\text{4}$) and acetylsanadol ($\text{5}$), isolated from $\text{Pachydictyon}$$\text{coriaceum}$, are determined, and sanadaol is produced by an acid-catalyzed ene reaction of dictyodial.     

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.     

Ring opening of benzoxazoles with allylic grignard reagents: synthesis of n-diallylalkyl-o-aminophenols.

The title benzoxales $\text{1a-d}$ react cleanly with allylic Grignard reagents $\text{2a-c}$ undergoing ring opening to give good yields of N-diallyl- alkyl-$\text{o}$-aminophenols $\text{3a-m}$. A plausible mechanism is discussed.     

Revision of the structure assigned to a monoterpene isolated from Piqueria trinervia

Unambiguous synthesis of 2-methyl-3-isopropenylanisole ($\text{1}$) and 2-isopropenyl-3-methylanisole ($\text{4}$) has led to revision, from ($\text{1}$) to ($\text{4}$), of the structure assigned to a monoterpene phenol ether isolated from $\text{Piqueria trinervia}$.     

Stereoselective total syntheses of (±)-sinularene and of (±)-5-epi-sinularene via intramolecular type-I-“magnesium-ene” reaction

(±)-Sinularene ($\text{1}$) as well as (±)-5-epi-sinularene ($\text{9}$) were synthesised in a stereocontrolled manner from the norbornene $\text{2}$ in overall yields of 4% and 8%, respectively. The key step $\text{5}$ → $\text{6}$ involves a regio- and stereoselective intramolecular “magnesium-ene” reaction.     

Reaction des acyloxy-2 chloro-3 chloromethyl-2 propanamides avec l'hydroxyde de potassium ou le fluorure de cesium en milieu heterogene synthese de spiro β-lactames

The reaction of cesium fluoride with the 2-acyloxy 3-chloro 2-chloromethylpropanamides ($\text{4}$) gave the 3-acyloxy 3-chloromethyl azetidine 2-ones ($\text{6}$) . Treated by powdered potassium hydroxide, $\text{4}$ and $\text{6}$ were converted into the 1-oxa 4-oxo 5-aza spiro (2,3) hexanes. These reactions in heterogeneous media were very selective and gave excellent yields.     

Synthesis of a flav-3-en-3-ol via cinnamylphenol

Vinyl quinone methide ($\text{1}$) reacts with polyphenols to give cinnamylphenols ($\text{4}$) and neo-flavanoids ($\text{5}$). Oxidation of cinnamylphenol ($\text{4}$b) leads to malvidin ($\text{10}$) via the isolated intermediate flav-3-en-3o1 ($\text{8}$b).     

Flexibly capped β-cyclodextrins by the hydrogen-bonded nucleic acid base pair. The pH-control of binding ability by an on-off-switched capping

Preparation and characterization of flexibly capped β-cyclodextrins ($\text{3a-c}$) by the hydrogen bonded nucleobase pair (i.e., adenine-thymine) are described.     

Stereoselektive synthese von α-glucosiden mit 1,1′ -diacetal-struktur

Reaction of ($\text{1b}$) and ($\text{1d}$) with the acetal ($\text{2a}$) in presence of trimethylsilyl trifluoromethanesulfonate at ?70° C gives the α-glucosides ($\text{3a}$) and ($\text{4a}$), whereas ($\text{1a}$) and ($\text{1c}$) lead to the β-glucosides ($\text{4c}$) and ($\text{4b}$). At 0° C reaction of ($\text{1a}$) with the acetals ($\text{2b-g}$) gives exclusively the α-glucosides ($\text{3b-g}$).     

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.