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.     

Flash vacuum thermolysis of spirocyclohexadienones

In an attempt to prepare short-bridged hydroxymetacyclophanes $\text{1b-d}$, the spirocyclohexadienones $\text{2b-d}$ were pyrolyzed by flash vacuum thermolysis (FVT). Instead of $\text{1b-d}$, variable amounts of 4-(5-hexenyl)phenol ($\text{4b}$), β-hydroxybenzocycloalkenes ($\text{5b-d}$) and 4-(trans-1-alkenyl) phenols ($\text{6c-d}$) were obtained. The formation of these products is explained by invoking cleavage of a spiro bond in $\text{2}$ under formation of the intermediate diradical $\text{3}$ which, depending on the length of the aliphatic chain and on the temperature, has several pathways open for isomerization to spin-paired products.     

The resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids

Practical procedures for the resolution of racemic modification of (1$\text{R}$, 2$\text{S}$)-and (1$\text{S}$, 2$\text{R}$)-1-amino-2-ethylcyclopropane-1-carboxylic acid $\text{1a}$,$\text{b}$,(1$\text{R}$, 2$\text{S}$)- and (1$\text{S}$, 2$\text{R}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{2a}$,$\text{b}$, and (1$\text{R}$, 2$\text{R}$)- and (1$\text{S}$, 2$\text{S}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{3a}$,$\text{b}$ are described; the structures as $\text{1a}$,$\text{2a}$, and $\text{3a}$ were confirmed by X-ray-crystallographic methods.     

Stereochemical studies 87saturated heterdcycles 82: Synthesis and steric structure of steredisomeric n-substituted tetrahydro-1,3-oxazines fused with norbornane or norbornene

$\text{diendo}$- and $\text{diexo}$-2-Methylamino and 2-benzylamino-3-hydroxymethylbicyclo [2.2.1]heptanes and the corresponding bicycio [2.2.1] heptenes ($\text{5a}$ -$\text{d}$, $\text{7a}$ -$\text{d}$) were synthesized from β-amino acid esters containing the norbornane or norbornene skeleton ($\text{3a}$-$\text{d}$). The aminoalcohols were converted to 5,8- methano -3,1-benzoxazines by reaction with formaldehyde. As established by ¹H and ¹³C NMR spectroscopy, the predominant conformation is $\text{endo - boat}$ ($\text{B}$) for the $\text{diexo}$, and $\text{exo - boat}$ ($\text{E}$) for the $\text{diendo}$ derivatives.     

A convenient synthesis of erythro- and threo-3-fluorophenyl- alanine from a protected glycine synthon

A facile synthesis of the title compounds ($\text{8}$ and $\text{9}$) is described; key steps include the mono-C-alkylation of the glycine Schiff base benzyl ester $\text{1a}$ with α-bromo-α-fluorotoluene, which provides the readily separable fluorinated diastereomers $\text{2a}$ and $\text{3a}$, and the dealkylative hydrolysis of the benzyl esters $\text{2a}$-$\text{5a}$ without concomitant loss of the benzylic fluorine.     

Aromatisierung von cytclohexenon-derivaten über selenorganische zwischenstufen

Reaction of the hydroaromatic compounds ($\text{1a}$) and ($\text{3a}$) with lithium-diisopropylamide followed by phenylselenenyl chloride gives the selenides ($\text{1b}$) and ($\text{1c}$) resp. ($\text{3b}$), which form exclusively the phenols ($\text{4}$) resp. ($\text{6}$) after oxidation with 3-chloroperbenzoic acid in the presence of 3,5-dimethoxyaniline ($\text{7a}$).     

Total syntheses of (±)-isoagatholactone and (±)-12α-hydroxyspongia-13(16),14-dien

(±)-Isoagatholactone $\text{1}$ and (±)-12α-hydroxyspongia-13(16),14-dien $\text{2b}$, a fundamental skeleton of spongiadiol $\text{2a}$ and its congeners, have been synthesized from (±)-labda-8(20),13-dien-15-oic acid $\text{3}$.     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Synthesis of enantiomerically enriched atrolactic acid and other α-hydroxy acids

The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid ($\text{2a}$, $\text{2b}$; $\text{3a}$; $\text{10a}$, $\text{10b}$) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-$\text{5}$,$\text{7}$,$\text{9}$, (R)(–)-$\text{13}$).     

Acid-catalysed reactions of 3,5-dialkyl-spiro[2.5]Octa-2,5-dien-4-ones

Acid-catalysed ring opening of the spirodienones ($\text{2a}$) and ($\text{2b}$) using p-toluene-sulphonic acid affords the styrène derivatives ($\text{3a}$) and ($\text{3b}$), while treatment with acetic anhydride/H₂SO₄ affords the furan derivatives ($\text{4a}$) and ($\text{4b}$).     

Synthesis,structure, and reactions of thiocarbonic acid derivatives new pentathiodipercarbonates, (RSS)2 CS, α,α,α-tris(disulfides), and the first α,α,α-tris(trisulfide)

Novel bis(perhaloalkyl) pentathiodipercarbonates $\text{5b-d}$ have been synthesized by reaction of sulfenyl chlorides with metal trithiocarbonates, and the heptathio analog $\text{21a}$ was prepared similarly. Lenthionine $\text{19}$ is the main product when diiodomethane is treated with sodium tetrathiopercarbonate. A rearrangement of bis(alkyldithio)chloromethanesulfenyl chlorides $\text{22}$ to alkyldithio) (alkyltrithio)dichloromethanes $\text{24}$ has been observed. Additions of sulfenyl chlorides and of thiosulfenyl chlorides to the thiocarbonyl compounds $\text{5}$ and $\text{21a}$ were achieved in acetonitrile. The structures of the first crystalline pentathiodipercarbonate $\text{5a}$ and α,α,α-tris(disulfide) $\text{29a}$, and of the first reported α,α,α-tris(trisulfide)$\text{31a}$ have been determined by X-ray crystallography.     

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.     

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 ($\text{3b-g}$).     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Acid catalyzed isomerization of bicyclic alkenes: a facile betweenanene synthesis

Isomerization of $\text{cis}$-bicyclo[10.8.0]eicos-1(12)-ene ($\text{1a}$) and $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene ($\text{1b}$) to [10.8]- and [10.10]betweenanene ($\text{2a}$ and $\text{2b}$) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 $\text{2a}$/$\text{1a}$ and 95/5> $\text{2b}$/$\text{1b}$).     

Cyclic acetals as carbonyl blocking groups in the photo-fries rearrangement of acyl substituted aryl esters.

The ethylene acetals of $\text{o}$ and $\text{p}$-acetoxyacetophenone 3a,b, prepared from the corresponding hydroxyacetophenones by treatment with acetic anhydride in pyridine and subsequently with ethylene glycol and $\text{p}$-toluenesulphonic acid, give upon irradiation the expected photo-Fries products 4a,b (from 3a) or 6 (from 3b). These compounds are converted in part into diacetylphenols 5a,b as a consequence of a deacetalization, occurring to some extent during the irradiation and further in the chromatographic workup. The yields of the photoproducts and the $\text{ortho}$/$\text{para}$ ratio (in the case of 3a) are very similar to those given in the literature for phenyl acetate. By contrast, the acetoxyacetophenones 2a,b do not undergo any appreciable change upon irradiation,showing the deactivating effect of the acetyl side chain. Therefore, it is concluded that cyclic acetals are suitable carbonyl blocking groups in order to circumvent the deactivating effect of acyl substituents on the photo-Fries rearrangement of aryl esters.     

Synthese und oxidation von 7-trifluormethylthiocycloheptatrien

Tropyliumbromide ($\text{1}$) reacts with AgSCF₃ to form 7-Trifluoromethylthiocycloheptatriene ($\text{6}$), which on oxidation with p-nitroperbenzoic acid does not form 7-Triflouromethylsulfonylcycloheptatriene ($\text{3a}$) but the trifluoromethylsulfinate ($\text{4a}$).     

Asymmetric synthesis of 2-substituted cycloalkanecarboxaldehydes

The 1,4-addition of Grignard reagents to chiral α,β-unsaturated cyclic aldimines ($\text{3}$), prepared from the corresponding cycloalkenecarboxaldehydes ($\text{1}$) and optically active α-amino acid tert-butyl esters ($\text{2}$, was found to give, after hydrolysis, trans-2-substituted cycloalkanecarboxaldehydes ($\text{5}$) in reasonably high enantiomeric purities.     

2-cyano Δ3 piperidines vi1 : a general method for the stereoselective synthesis of cis and trans 2,6-dialkylpiperidine alkaloids

The cis 2,6-dialkylpiperidine alkaloid (±) dihydro-pinidine $\text{7b}$ and the trans alkaloid (±) solenopsin A $\text{5a}$ were synthesized from a common α-aminonitrile synthon $\text{1}$. The key step in this synthesis was the stereoselective reductive decyanation of the 1-benzyl-2cyano-2′, 6-dialkylpiperidines $\text{3a}$ and $\text{3b}$.