Some approaches to the synthesis of fluorinated alcohols and esters. III. Synthesis of 2-(F-alkyl)ethanols from 2-(F-alkyl)-1-iodoethanes and amides.

1-Iodo-2-(F-alkyl)ethanes, R_FCH₂CH₂I, when heated with a large excess of N-methylformamide (NMF) give in high yield, mixtures of predominately R_FCH₂CH₂OH, some formate ester and a little R_FCHCH₂. In a study of this process, significant variables were examined, including solvent, reactant ratio, effect of water, and alternative amide reactants. The coproduct from NMF is the amidine salt, [MeNHCH(NHMe)]⁺I⁻. By contrast, R_FCH₂CH₂I with N,N-dimethylformamide (DMF) and water (one or two mols) gives chiefly the formate ester; the coproduct is Me₂NH₂⁺I⁻. A mechanistic scheme is proposed: in the first step, an alkyl imidate salt, e.g., [HC(NH Me)OCH₂CH₂R_F]⁺I⁻ is formed by O-alkylation of NMF; reaction of the imidate with more NMF gives a tetrahedral intermediate that breaks down rapidly to R_FCH₂CH₂OH, and HC(NHMe)NMeCHO⁺I⁻. The formate ester is derived from the alcohol and this N-formyl acylating agent, in a subsequent step. Analogously, the alkyl imidate salt from DMF and R_FCH₂CH₂I reacts with water as nucleophile (but not with DMF) to give a tetrahedral intermediate that cleaves under stereoelectronic control to formate ester and amine salt, but not to alcohol. Quantitative isolation of amine salt and amidine salt, and observed rates of reaction give solid support to this proposed mechanism.     

Studies on sulfinatodehalogenation XXIII. A new sulfinatodehalogenation reagent: thihurea dioxide1

HSO₂^? generated from thiourea dioxide and sodium bicarbonate in aqueous CH₃CN at 35–45°C reacted with perfluoroalkyl iodides, polyfluoroalkyl bromide, 1,1,1-trichloro-2,2,2-tri-fluoroethane and carbon tetrachloride to give the corresponding sulfinates in good yield. Furthermore, it was shown that the reagent was able to initiate the addition of perfluoroalkyl iodide to olefins and alkynes at 30°C.     

A convenient and diastereoselective route to homoallyl alcohols: Addition of (z)- or (e)-alkenyl-dimethoxyboranes to aldehydes

(Z)-2-Butenyl-dimethoxyborane adds smoothly to propanal and benzaldehyde to afford the homoallyl alcohols (R*,R*)- 1 and (R*,R*)- 2 , In contrast (E)-2-butenyl-dimethoxyborane leads to adducts having the (R*,S*)-configuration. Dimethoxy-(Z)-2-pentenylborane, dimethoxy-(Z)-(2-methyl-2-butenyl)borane and (2Z,4E)-or (2E,4Z)hexadienyl-dimethoxyborane, treated with propanal, give (R*,R*)- 3 , (R*,R*)- 4 , (E),(R*,S*)- 5 and (Z),(R*, R*)- 5 , respectively. A transition state model implying a pericyclic electron motion is in perfect agreement with the regio- and stereoselective outcome of these borane reactions.     

Spectroscopic calculations of CH and OH bond dissociation energies for aldehydes, ketones, acids, and alcohols

CH and OH bond dissociation energies were calculated by the spectroscopic and quantum-chemical methods for aldehydes, ketones, acids, and alcohols. The spectroscopic values of CH and OH bond dissociation energies were obtained from the fundamental absorption bands by the variational method in an anharmonic approximation using the Morse-anharmonic basis set. Quantum-chemical calculations were carried out using the 6-311G(3df,3pd)/B3LYP basis set. It is discussed how the bond dissociation energies change with the structure of the molecule.     

tert-Butylnitrite as a convenient and easy-removable oxidant for the conversion of benzylic alcohols to ketones and aldehydes

The oxidation of primary and secondary benzylic alcohols was achieved by using tert-butyl nitrite (t-BuONO) as a stoichiometric oxidant. Various substrates were effectively converted into the corresponding ketones or aldehydes in good to excellent yields. The reaction presumably proceeded by a nitrosyl exchange and a subsequent thermal decomposition of benzylic nitrites. This process would realize an oxidation of alcohols with oxygen in theory by combining with a reproduction of alkyl nitrites from NO and alcohols under an O₂ atmosphere. In addition, almost pure oxidized products were readily obtained by simple evaporation of the reaction mixtures since t-BuONO produced only volatile side products.     

Studies on sulfinatodehalogenation XIII. A new sulfinatodehalogenation reagent system: NaHSO3/K3[Fe(CN)6]

The reaction of perfluoroalkyl iodide or perfluoroalkyl bromide with sulfite radical anion (SO₂) generated from sodium bisulfite / potassium ferricyanide in water/ DMF at 70—75°C gave the corresponding perfluoroalkanesulfinate in good yield. Furthermore, it was shown that the reagent system can also initiate the addition of perfluoroalkyl iodide to olefins or alkynes at 50—65°C.     

Indium-mediated allylation of aldehydes, ketones and sulfonimines with 2-(alkoxy)allyl bromides

2-(Alkoxy)propenyl bromides are readily prepared from 1,3-dibromo-2-propanol in a two-step sequence involving hydroxyl protection and sodium hydride-induced dehydrobromination. Indium-mediated allylation of aldehydes, ketones, and sulfonimines with 2-(alkoxy)propenyl bromides furnishes the corresponding homoallylic alcohols and sulfonamines in good yields. The products can be easily transformed into β-hydroxy ketones and esters, as well as substituted dihydropyrans, and protected β-amino acids. Chiral 2-(alkoxy)propenyl halides, derived from (−)-menthol and d-glucal, furnish diastereomerically enriched products.     

A convenient method for the preparation ofN-unsubstituted hydrazones of aromatic ketones and aldehydes

A general and useful method for the synthesis ofN-unsubstituted hydrazones of aromatic ketones and aldehydes in good yields was elaborated. The use of a large excess of hydrazine hydrate and catalytic amounts ofp-toluenesulfonic acid makes it possible to prepare the hydrazones without an admixture of the corresponding azine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2199, November, 1999.     

A convenient semicarbazide resin for the solid-phase synthesis of peptide ketones and aldehydes

Use of a semicarbazide resin for the solid-phase preparation of peptide ketones and aldehyde led to optimal results in terms of both purity of the final product and overall yield. This resin was prepared without complication by activation of the commercial available aminomethyl polystyrene with CDI at room temperature, followed by treatment with tert-butyl carbazate. Furthermore, the TNBSA colorimetric assay has been adapted for checking the incorporation of the carbonyl moiety onto hydrazine-based resins.     

Step by step palladium mediated syntheses of new 2-(pyridin-2-yl)-6-R-nicotinic acids and esters

Taking advantage of palladium peculiar “rollover” C,N cyclometallation, it is possible to promote C(3) functionalization of 6-alkyl-substituted-2,2′-bipyridines. The carbonylation reaction of rollover species [Pd(Lⁿ)Cl]₂, (HL¹ = 6-isopropyl-2,2′-bipy, 1; HL² = 6-neopentyl-2,2′-bipy, 2; HL³ = 6-ethyl-2,2′-bipy, 3; HL⁴ = 6-methyl-2,2′-bipy, 4) allowed the synthesis of 2-(pyridin-2-yl)-6-alkyl-nicotinic acids or esters. These nicotinic derivatives are extremely rare and, as far as we know, quite unreported in the case of the 6-substituted molecules.     

Bis(trimethylsilyl)chromate catalyzed oxidations of alcohols to aldehydes and ketones with periodic acid

A facile, selective and high yielding bis(trimethylsilyl) chromate (BTSC) catalyzed selective oxidation of alcohols to aldehydes and ketones with periodic acid is reported.     

Reaction loops for reaction Gas chromatography. Subtraction of alcohols,aldehydes, ketones,epoxides, and acids and carbon-skeleton vchromatography of polar compounds

Summary Reaction loops may be used in a gas Chromatographic system to help determine the chemical structure of compounds. Loops that retain or detain compounds with a certain functional group subtract these compounds and thereby indicate the presence of the functional group in unknown compounds. The performance of loops in subtracting alcohols, acids, aldehydes, ketones, epoxides, and a variety of other compounds was studied to amplify the usefulness of this technique. A simplified version of carbon-skeleton chromatography was also shown to be useful for analysis of polar or high molecular weight compounds (C₁₂ or higher).

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Zusammenfassung Reaktionsschleifen können sich in gaschromatographischen Geräten für die Ermittlung der chemischen Struktur von Verbindungen als nützlich erweisen. In diesen Schleifen werden Verbindungen mit einer bestimmten funktionellen Gruppe zurückgehalten, deren Vorhandensein in unbekannten Verbindungen damit indiziert wird. Die Wirkungsweise solcher Schleifen bei der Entfernung von Alkoholen, Säuren, Aldehyden, Ketonen, Epoxiden und verschiedenen anderen Verbindungen wurde studiert, um die Brauchbarkeit dieser Methodik zu erweitern. Eine einfachere Form der Kohlenwasserstoff-Chromatographie hat sich gleichfalls als wertvoll für die Analyse polarer oder Verbindungen mit hohem Molekulargewicht (C₁₂ oder höher) erwiesen.

     

A new glycociamidine ring precursor: syntheses of (Z)-hymenialdisine, (Z)-2-debromohymenialdisine, and (+/-)-endo-2-debromohymenialdisine

[chemical reaction: see text]. The synthesis of the C11H5 marine sponge alkaloids, (Z)-hymenialdisine and (Z)-2-debromohymenialdisine, is described. A key step was the condensation between aldisine or its monobromo derivative and a new, efficient imidazolinone-based glycociamidine precursor. In the first case, the main product turned out to be the unprecedented (+/-)-endo-2-debromohymenialdisine.     

Pd(ii)-hydrotalcite-catalyzed oxidation of alcohols to aldehydes and ketones using atmospheric pressure of air

A heterogenized Pd catalyst, Pd(II)-hydrotalcite (palladium(II) acetate-pyridine complex supported by hydrotalcite) catalyzes the aerobic oxidation in toluene of a variety of primary and secondary alcohols into the corresponding aldehydes and ketones in high yields using atmospheric pressure of air as a sole oxidant under mild conditions. This catalyst is also effective for the oxidation of allylic alcohols, especially such as geraniol and nerol, without any isomerization of an alkenic part. The catalyst can be easily prepared from all commercially available reagents and reused several times.     

Studies on pyrrolidinones. A convenient synthesis of 2-methyl-5-(5-oxo-1-benzyl-2-pyrrolidinyl)-1,3,4-oxadiazole

2-Methyl-5-(5-oxo-1-benzyl-2-pyrrolidinyl)-1,3,4-oxadiazole is easily obtained by dehydration of N-acetyl-1-benzylpyroglutamic acid hydrazide with a methanesulfonic acid/phosphoric anhydride mixture.