Mechanisms for reactions of halogenated compounds. Part 4.[1] activating influences of ring-nitrogen and trifluoromethyl in nucleophilic aromatic substitution

Rate constants have been measured for the reactions of ammonia with various fluorinated pyridines and diazines in aqueous dioxan at 25°. From the results the activating effects of ring-nitrogen (relative to CH) and of trifluoromethyl (relative to -H) have been determined. Ring-nitrogen activates the system at points $\text{ortho}$-, $\text{meta}$- and $\text{para}$- to the point of substitution, in the ratios $\text{ortho}$- 6.2 × 10⁴, $\text{meta}$- 8.5 × 10², and $\text{para}$- 2.3 × 10⁵. Similarly a trifluoromethyl substituent is activating by a factor of 2.4 × 10³$\text{ortho}$- and 4.5 × 10³$\text{para}$- to the point of substitution.     

Synthesis of 4″-carboxylated cannabinoids: Stereospecific processes involving ethylidenemalonic ester

4″-Carboxylated-cannabidiol,-Δ¹-and-Δ^1,6-tetrahydrocannabinols and - cannabinol are synthesised. Condensation between aromatic aldehydes and ethylidenemalonic ester gives a 2$\text{E}$,4$\text{E}$-half ester stereospecifically, a reaction which can be used to make 2$\text{E}$-4$\text{E}$- or 2$\text{Z}$,4$\text{E}$-pentadienoates.     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

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.     

Bis(tricarbonyliron) complexes of P-quinodimethanes: fragmentation and isomerisation under electron impact

EI mass spectra of $\text{trans}$-η⁴,η⁴-[3,6-bis(methylene)-1,4-cyclohexadiene]-bis=(tricarbonyliron) complexes $\text{1a}$, $\text{b}$ are reported. The fragmentation pathway is rationalized by assuming a rearrangement of the $\text{trans}$-bis(tricarbonyliron) complexes into the $\text{cis}$-isomers under electron impact.     

Boat-chair conformational preference of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

The ¹H and ¹³C nmr spectra of $\text{exo}$, $\text{exo}$-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d₆ or alkaline D₂O, clearly show that it exists in a $\text{boat}$-$\text{chair}$-conformation with $\text{equatorial}$ carboxyl groups, thus being the first case of $\text{boat}$-$\text{chair}$ preference of a bicyclo[3.3.1] nonan-9-one due to the presence of $\text{exo}$,$\text{exo}$-2,4- substituents.     

1,1-Diaminosubstituted 2-azaallenium salts: preparation and barriers to topomerization

Dialkylcarbodiimides, $\text{5}$, react with iminium salts, $\text{6}$, to afford the formal 1,1-diaminosubstituted 2-azaallenium salts $\text{3}$. According to dynamic NMR measurements compounds $\text{3}$ must be regarded as alkylidene-guanidinium salts $\text{A}$, undergoing a fast topomerization via a transition state $\text{B}$ with allene geometry (2G⁼₂₆₅ = 45.9 ± 1 kJmol^-1 for $\text{3f}$) and a slower rotation around the peripheral C-N bonds (transition state $\text{C}$; 2G⁼₂₉₀⁼ 58.0 ± 1 kJmol^-1 for $\text{3f}$).     

Ligand exchange reactions of ferrocene with phenanthrene or 9,10-dimethylphenanthrene in the presence of aluminum chloride and aluminum

Ligand exchange reactions between phenanthrene or 9,10-dimethylphenanthrene with ferrocene effected in the presence of AlCl₃-Al were carried out under a variety of conditions. With phenanthrene (I), hydrogenation at the C-9 and C-10 positions could take place during the reaction and the cationic products obtained were the η⁶-phenanthrene-η⁵-cyclopentadienyliron and η⁶-9,10-dihydro-phenanthrene-η⁵-cyclopentadienyliron moncations (II and III), and the η⁶-phenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron and η⁶-9,10-dihydrophenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dications (IV and V). With 9,10-dimethylphenanthrene (VI), reactions carried out in refluxing cyclohexane gave the non-hydrogenated η⁶-9,10-dimethylphenanthrene-η⁵-cyclopentadienyliron monocation (VII) and η⁶-9,10-dimethylphenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dication (VIII). When higher temperatures were used in an attempt to promote hydrogenation, decomposition predominated and no cationic product could be obtained. These finding are discussed and contrasted with previous results obtained from similar reactions using anthracene or 9,10-dimethylanthracene.     

Conformational dependence of pyranoid rings 1,2-cis-fused to dioxolane rings on the configuration of the dioxolane rings in acetylated derivati

X-Ray and ¹H N.M.R. studies on pyranoid rings 1,2-$\text{cis}$-fused to dioxolane rings in acetylated $\text{D}$-gluco- and $\text{D}$--galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the $\text{D}$-gluco but not in the $\text{D}$-galactopyranose series. The crystal structure of 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-(R)--(l-cyano-ethylidene)-α-$\text{D}$-glucopyranose ($\text{1}$) and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{R}$)-(1-cyano-ethylidene)-α-$\text{D}$-galactopyranose ($\text{2}$)have been determined by X-ray analysis. Lattice parameters for $\text{1}$ are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for $\text{2}$ are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened ⁴C₁ and that of the dioxolane ring as distorted E₁. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The ¹H N.M.R. spectra of $\text{1}$ and $\text{2}$ and 3,4,6-tri-$\text{O}$-acetyl-1,2-O-(S)- and (R)-ethylidene-α-$\text{D}$-glucopyranose ($\text{5}$ and $\text{7}$), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ($\text{R}$)-ethylidene-α-$\text{D}$-galactopyranose ($\text{6}$ and $\text{8}$), and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{S}$)-and ($\text{R}$)-benzylidene-α-$\text{D}$-glucopyranose ($\text{9}$ and $\text{10}$) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the $\text{D}$-gluco series $\text{1}$, $\text{5}$ and $\text{9}$ may be described as flattened ⁴C₁ and that of $\text{7}$ and $\text{10}$ as ²$\text{S}$₅. The major solution conformation of the pyranoid ring in all compounds in the $\text{D}$-galacto series ($\text{2}$,$\text{4}$,$\text{6}$,$\text{8}$) may be described as flattened ⁴$\text{C}$₁.     

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.     

Zwei neue pentacyclische dimere des cycloheptatriens

Titanium - catalyzed dimerization of cycloheptatriene affords pentacyclo[7.5.0.0^2,8.0^5,14.0^7,11]tetradeca-3,12-diene, $\text{3}$, and pentacyclo[8.4.0.0^3,7.0^4,14.0^6,11]tetradeca-8,12-diene, $\text{4}$. By heating, $\text{3}$ is converted quantitatively into $\text{4}$.     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

Synthesis and absolute configuration of +-lineatin,the pheromone of trypodendronlineatum

A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.0^4,7] nonane, $\text{1}$) was achieved. The stereochemistry of (+)-lineatin was established as 1$\text{R}$, 4$\text{S}$, 5$\text{R}$, 7$\text{R}$ by an X-ray crystallographic analysis of an intermediate $\text{1}$$\text{5}$.     

Activation and transfer of oxygen XV evidence for the transient opening of the pyrazine ring in n1- and n5- alkylflavin models. 4a- to 1010- adduct isomerization and pyrazine- and pyrimidine- ring contractions.

The pyrazine ring opening is proven by rearrangements leading to benzimidazoles $\text{4}$, $\text{13}$ and $\text{14}$. A 4^a- to 10^a-adduct isomerization ($\text{6}$ → $\text{7}$) and the intermediacy of a carbonyl oxide $\text{15}$ are indicated by pyrimidine ring contractions into $\text{8}$ and $\text{9}$, respectively.     

The Stereochemistry of simple enols in solution

On the basis of their ¹H n.m.r. spectra it is concluded that vinyl alcohol and $\text{trans}$-1-propenol exist mainly in the $\text{syn}$-conformation and that $\text{cis}$-1-propenol and 2-methyl-1-propenyl exist mainly in the $\text{anti}$ conformation.     

Isolation and structural elucidation of heliangolidin,a new sesquiterpene lactone from artemisia canariensis

A new heliangolide has been isolated from aerial parts of $\text{Artemisia canariensis}$, and identified as (6$\text{E}$,10$\text{Z}$)(3$\text{S}$,3a$\text{R}$,4$\text{S}$,lla$\text{R}$)-3a,5,8,11a--tetrahydro-4-acetoxy-3,6, 1O-trimethyl-2,9 (3$\text{H}$, 4$\text{H}$) -cyclodeca[b] furandione. The structural elucidation of the new compound, named heliangolidin, was carried out by spectral means (MS, IR, ¹H and ¹³C NMR, and two dimensional ¹H-¹³C chemical shift correlations) and X-ray diffraction analysis.     

The reaction of vinyl azides with sulfoxonium ylids. Synthesis of n-vinyl triazolines and vinyl aziridines.

Vinyl azides $\text{1}$ react with dimethylsulfoxonium ylid $\text{3}$ at the azide function to produce in high yield 1-vinyl-4,5-unsubstituted-Δ-1,²-1,2,3-triazolines $\text{4}$. Vacuum flash pyrolysis of $\text{4}$ furnished N-vinylaziridines $\text{7}$ without formation of pyrolines.     

Synthesis of both 2,3-erythro- and 2,3-threo- isomers of aplidiasphingosine,a bioactive marine terpenoid

2,3-$\text{threo}$- and 13,14-$\text{erythro}$-Relative configurations were proposed for aplidiasphingosine by synthesizing both its 2,3-erythro- and 2,3-$\text{threo}$- isomers and examining their ¹³c-NMR spectra.     

Circular dichroism of α-deuteriocarboxylic acids. Dissignate behavior of deuterium.

Positive n → π^* Cotton effects were shown by ($\text{S}$-2-deuteriopropionic acid, ($\text{S}$)-2-deuteriosuccinic acid, ($\text{R}$)-2-deuterioglycine and ($\text{R}$)-2-deuterioglycolic acid. Using an octant projection and conformational and chiroptical data, it can be shown that the deuterium substituent makes a dissignate contribution to the Cotton effect.     

Exo/emdo soltolysis rate ratios in constrained 2-norbornyl systems

Tetracyclol[6.2.1.0^2,6.0^5,10]undec-3-yl derivatives ($\text{6}$ - $\text{8}$) show typically high tertiary exo/endo solvolysis rate ratios, but the ratios for secondary reactants are suppressed. The rate and product data support the theory of anchimeric assistance in the parent $\text{exo}$-2-norbornyl solvolysis.