Synthesis and crystal structure of a π-allyl iron carbonyl complex derived from a fluorocarbon containing ligand by loss of fluorine

The β-chlorovinylphosphines R₂P$\text{C  CCl(C}$F₂)₃ (R = C₆H₅, C₆H₁₁) react with Fe(CO)₅ yielding compounds of stoichiometry

. The crystal structure of one of these (R = C₆H₁₁) has been determined from X-ray diffraction data and refined by least-squares to $\text{R}$ = 0.037 (2313 reflections with $\text{I}$ > 2.3σ_$\text{I}$). Crystals are triclinic, space group $\text{P}$$\text{1}$, $\text{a}$ = 10.253(5), $\text{b}$ = 15.590(7), $\text{c}$ = 9.390(4)Å, α = 99.88(3), β = 103.21(2), γ = 92.02(2)°, $\text{Z}$ = 2. The fluorinated π-allyl group is σ-bonded to one Fe atom and π-bonded to the other.     

Condensation of a p-diazooxide with dimethyl acetylenedicarboxylate: formation of a spiro [4.5] Decatetraenone and a nonenolizable naphthalenone in a single reaction

The condensation of p-diazooxide $\text{1}$ with dimethyl acetylenedicarboxylate at 90°–100°C yields two C₂₆H₃₂O₉ products, corresponding to addition of two molecules of ester to one of the carbene $\text{2}$. The major product is the novel spirodecatetraenone $\text{4}$, and the minor product is the remarkable, nonenolizable naphthalenone $\text{5}$. Spirodecatetraenone $\text{4}$ is not a precursor of $\text{5}$, since the former is stable to acids and rearranges only above 200° to give the blocked azulenone $\text{8}$. A mechanism for the concomitant formation of product $\text{4}$ and $\text{5}$ is proposed.     

Chemically reacting bismuth and nitrous oxide in a heat pipe oven

The chemical reactions between bismuth and oxidants in a heat pipe oven are described. Strong chemiluminescence (A²Π_{$\text{1}\text{2}$} → X²Π_{$\text{1}\text{2}$}) was observed in the reaction with N₂O and the vibrational temperature of the A²Π_{$\text{1}\text{2}$} state was measured to be 3150 ± 300 K.     

Synthesis,Reactions and Catalytic Activities of a Cationic Acrylonitrile-Rhodium(I) Complex

Reaction of RhCl (CO)(Ph₃P)₂(Ph₃P = triphenylphosphine) with AgClO₄ in acrylonitrile at 30°C produces a new cationic rhodium(I) complex, [Rh(CH₂CHCN)(CO) (Ph₃P)₂]ClO₄ ($\text{1}$) and AgCl. The ¹H-NMR and IR spectra of $\text{1}$ suggest that acrylonitrile is coordinated to rhodium through the π-system of the vinyl group. The complex $\text{1}$ reacts with molecular hydrogen to give a propionitrile-rhodium(I) complex, [Rh(CH₃ CH₂CN) (CO)(Ph₃P)₂ClO₄($\text{2}$) where the coordination of propionitrile through nitrogen is suggested by the ¹H-NMR and IR spectral data. The coordinated acrylonitrile in $\text{1}$ is readily replaced with triphenylphosphine and propionitrile to give [Rh(CO)(Ph₃P)₃] ClO₄ and $\text{2}$, respectively. The complex $\text{1}$ is catalytically active for the hydrogenation and polymerization of acrylonitrile at 25°C under the atmospheric pressure of hydrogen.     

Nitroindolenines en serie vincadifformine : intermediaires d'acces a la vincamone et a un squelette azahomoaspidospermane

Vincadifformine and its 10-substituted analogs give in good yields 16-nitro indolenines of which the reactivity has been studied. By a two step process (demethoxycarbonylation and chloration on C16) nitro-indolenine $\text{2b}$ leads to gem-chloro-nitro $\text{6}$. By an other two step sequence (NaBH₃CN, NaH) nitro-indo-lenine $\text{2c}$ yields compound $\text{10}$ via a 16 → 1 COOCH₃ migration. By heating compounds $\text{6}$ and $\text{10}$ in CF₃COOH, rearranged products are obtained : vincamione $\text{5}$ from $\text{6}$ and azahomoaspidospermane $\text{13}$ from $\text{18}$. Mechanisms of formation of $\text{5}$, $\text{10}$ and $\text{13}$ are discussed.     

An approach to the enantiocontrolled synthesis of pseudomonic acids via a novel mono—claisen rearrangement

A short, efficient approach to a key chiral intermediate for the synthesis of pseudomonic acids A and C is delineated.Pseudomonic acids A($\text{1a}$), B($\text{1b}$), and C($\text{2}$) are members of a novel of “C-glycopyranoside” antimicrobial agents which have recently attracted synthetic attetion.² Presently, we wish to report a short efficient stratedy towards the total synthesis of opticaly active pseudomonic acids. The sequence is highlighted by a novel controlled mono-Claisen rearrangement and a highly regioselective π-allylpalladium mediated displacement.Diacetyl-(L)-arabinal ($\text{3}$)³ was converted to the bis-ketenesilylacetal $\text{4}$ and warmed to 60°C according to the Ireland ester-enolate Claisen rearrangement method.⁴ Over a period of ≈5h, smooth conversion to a major rearranged product $\text{5}$ was observed by 300 MHz NMR. The identity of $\text{5}$ was confirmed by direct desilylation and methylation (KF, KHCO₃, H₂O, HMPA, CH₃I). After flash chromatography, compound $\text{7}$ was isolated in 55% overall yield from $\text{3}$. Careful inspection of the crude methylation product revealed the presence of ≈5% doubly rearranged product $\text{6}$.The rearrangement of $\text{4}$ to $\text{5}$ is a unique example of a selective mono-Claisen rearrangement in which the rate of a second similar Claisen rearrangement ($\text{5}$ → $\text{6}$) is much slower under the reaction conditions. Although the reasons for this interesting selectivity are unclear at this time,⁵ in practice, the mono-Claisen rearrangement obviates the need for selective differentiation of the two hydroxyl groups, a difficult task at best, in this case.Palladium mediated allylic acetate displacement provided an ideal method for introduction of a second chemodifferentiated side chain with allylic retention and retention of stereochemistry. Alkylation of $\text{7}$ with sodiothylmalonate using 5 mole % Pd(O)dppe₂⁶ was unusually facile (<45 min, 25°C, THF). After semi-preparative HPLC, essentially a single regio- and stereoisomer was isolated in 96% yield.⁷ Structure $\text{8}$ was confirmed by extensive ¹H-NMR decoupling, as well as an off-resonance ¹³C-NMR experiment. In particular, H₁ (δ 4.53) was coupled vicinally to H₆ and H₆′ (5 Hz, 8 Hz) and H₂ (1.5 Hz), and allylically to H₃ (2 Hz). In contrast, H₄ (δ 2.78) was coupled to H₇ (10 Hz), H_5e and H_5a (1.8 Hz, 4 Hz), H₃ (5 Hz), and H₂ (<1 Hz). In addition, H₁ and H₄ exhibited a small long range coupling constant (J = <1 Hz). The coupling constants rule out

regioisomer $\text{9}$ and are fully consistent with the indicated conformation, which minimizes 1,3-diaxial-like interactions.Finally, catalytic osmylation of $\text{8}{}^8$ gave a single cis-diol $\text{10}$ in nearly quantitative yield. Appending of suitably functionalized side chains to provide an enantiocontrolled synthesis of pseudomonic acids A($\text{1a}$) and C($\text{2}$) is in progress.^9,10     

Structure of HC-toxin,a cyclic tetrapeptide from helminthosporium carbonum

$\text{Helminthosporium carbonum}$, which is pathogenic to maize, produces a metabolite, HC-toxin ($\text{1}$), with selective toxicity to susceptible host genotypes. Resistant genotypes and non host plants are tolerant. The structure of $\text{1}$ (C₂₁H₃₂N₄O₆) was determined as cyclo [(2-amino-9,10-epoxy-8-oxodecanoyl)-alanyl-alanyl-prolyl] based upon spectral evidence.     

Addition of trimethylsilyllithium and trimethylstannyllithium to a hindered cyclopropyl enone

Addition of Me₃SiLi or Me₃SaLi to $\text{1}$ affords cyclopropyl cleavage to the ring expanded system ($\text{2}$ and $\text{3}$).     

Singulett-Sauerstoff-induzierte spaltung von spiro[1,8a]dihydroindolizinen

The ¹O₂-induced degradation of spiro[1,8a]dihydroindolizines $\text{1}$ - a new photochromic system - may involve dioxetanes as intermediates giving fulvenylesters $\text{3}$.     

Active manganese dioxide: a reagent for a biomimetic cyclization of 16β-hydroxylated 22.26-epiminocholestanes to spirosolane alkaloids

Treatment of the 16β-hydroxylated 22.26-epiminocholestanes $\text{1}$ - $\text{4}$ with activated MnO₂ leads in a biogenetically remarkable cyclization directly and in good yields to the corresponding spirosolane alkaloids $\text{5}$ - $\text{8}$.     

Trimethymetall-urotropinaddukte des aluminiums,galliums, indiums und thalliums

Reactions of urotropine (C₆H₁₂N₄) with trimethylmetal derivatives of Al, Ga, In und Tl in various ($\text{1}\text{1}$$\text{1}\text{4}$) molar ratios lead to stable and monomeric $\text{1}\text{1}$, $\text{1}\text{2}$ or $\text{1}\text{3}$ adducts in good yields, but no $\text{1}\text{4}$ addition product could be isolated. The vibrational spectra (IR and Raman) of all compounds are recorded and partly assigned. Some characteristic frequencies of the C₆N₄-skeletons clearly show the symmetry changes in the series of the $\text{1}\text{1}$ → $\text{1}\text{2}$ → $\text{1}\text{3}$ adducts (C_3ν → C_2ν → C_3ν). The X-ray structure determinations of C₆H₁₂N₄·.GaMe₃ (MeCH₃) and C₆H₁₂N₄·.2GaMe₃, are in good agreement with the vibrational spectra. Both compounds crystallize in monoclinic space groups (P2₁ and C2/c). The GaN distances are around 214 pm, and the values for the C₆N₄-skeletons are not significantly different from those for free urotropine.     

Isolation of aspirochlorine (=antibiotic A30641) possessing a novel dithiodiketopiperazine structure from Aspergillus Flavus

A very unusual dithiokikeptopiperazine structure ($\text{1}$) has been assigned to aspiroclorine, C₉H₁₂N₂O₅S₂Cl, produced as a biologically active substance together with canadensolide by $\text{Aspergillus}$$\text{flavus}$, which has been found to be identical with the antibiotic A 30641 from $\text{A.}$$\text{tamarii}$.     

Nucleophilic reactions of fluoroolefins. II. Regioselectivity and elimination-addition competition in the reaction of 1-phenylpentafluoropropenes with sodium ethoxide

1-Phenylpentafluoropropene and its para-substituted analogs $\text{1}$ are susceptible to nucleophilic attack at both vinylic carbon atoms C-1 and C-2. They react with ethanolio sodium ethoxide to give predominantly substitution products, 1-ethoxy-1-phenyltetrafluoropropenes $\text{2}$ and 2-ethoxy-1-phenyltetrafluoropropenes $\text{3}$, with only little formation of adducts, $\text{viz}$. 2-ethoxy-1H-1-phenylpentafluoropropanes $\text{4}$. Alkenes $\text{1}$, where the para-substituent X  H,Cl,and CF₃ give additionally 1,2-diethoxy-1-phenyltrifluoropropenes $\text{5}$ and, where X = CF₃ also 2,2-diethoxy-1H-1-phenyltetrafluoropropane $\text{6}$. Overall regioselectivity of nucleophilic attack of the ethoxide ion on alkenes $\text{1}$ exhibits the Hammett type correlation with Ó_p values of substituents X: CH₃O and CH₃ groups favour the attack on the vinylic carbon C-1, while CF₃ and Cl substituents direct the attack on the C-2 carbon of alkenes $\text{1}$. The E and Z isomers of 1-ethoxy and 1,2-diethoxy substituted alkenes $\text{2}$ and $\text{5}$ were formed in comparable amounts, while the E isomers of 2-ethoxy substituted alkenes $\text{3}$ were always formed with a 93 – 97 % selectivity.     

Asymmetric synthesis via acetal templates. 12. Highly diastereoselective coupling reactions with a ketene acetal. An efficient,asymmetric synthesis of R-(+)-α-lipoic acid

TiCl₄ catalyzes the essentially quantitative coupling of chiral acetals $\text{1}$ with 1-$\text{t}$-butoxy-1-$\text{t}$-butyldimethylsilyloxyethene $\text{2}$ to generate β-alkoxycarboxylates in which the new asymmetric center is formed with excellent diastereoselection. β-hydroxycarboxylic acids of high ee result from removal of the chiral auxiliary. The procedure has been applied to the synthesis of R-(+)-α-lipoic acid $\text{10.}$     

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.     

The thiolate anion as a nucleophile Part XI. Effect of the size of the nucleophile

The nucleophilic substitution reactions of some simple fluorobenzenes, C₆H_6?xF_x with sodium methanethiolates Na⁺SR^?(R=Et, $\text{i}$-Pr, $\text{t}$-Bu) have been studied. Some fully substituted products, C₆H_6?x(SR)_x, could be obtained in DMF as solvent with R = Et and $\text{i}$-Pr, but not when R = $\text{t}$-Bu. All the new products isolated have been characterized by elemental analysis, and NMR (H-1 and F-19), infrared and mass spectroscopy.     

Micellar alkylation: a methylating surfactant

Micellar $\text{n}$-C₁₆H₃₃$\text{N}\text{+}$(CH₃)₂CH₂$\text{S}\text{+}$(CH₃)₂, 2CF₃SO₃^? rapidly methylates bound thiophenoxide ions.     

Nuclear analogs of β-lactam antibiotics 8. Stereospecific synthesis of a C-3 methoxylated monocyclic s-lactam

Methoxylation of $\text{1}$(R = PhOCH₂CO) occurred stereospecifically from the α-face as determined by x-ray crystallography to provide $\text{2}$ which was converted to $\text{4}$ whose $\text{in}$$\text{vitro}$ antimicrobial activity was determined.     

Rotational and vibrational temperatures of naphthalene in a naphthalene-argon supersonic jet

In the $\text{A}$¹B_2u-$\text{X}$¹A_g system of naphthalene in a supersonic jet, rotational contour calculations show rotational temperatures of 2–60 K for argon carrier gas pressures of 1520-120 Torr. The b_1u vibration v₂₄ shows a high vibrational temperature which corresponds to the seeding temperature for pressures <400 Torr.     

[2+2]-Cycloadditionen von vinylkationen

The vinylbromides $\text{1a}$ and $\text{1b}$ are allowed to react ith AgBF₄ and AgPF₆ in the presence of various olefins in CH₂Cl₂ as the solvent. Except for the reaction of cyclopentene with $\text{1a}$ all other olefins used, react with vinyl cation $\text{2}$ to form the cycloaddition products $\text{7}$, $\text{8a}$ and $\text{8b}$ in high yields.