Fluoroaconitates: Wittig Reaction of Oxalofluoroacetic Acid Esters

Triphenylcarboalcoxymethylene phosphoranes 1 are condensed with oxalofluoroacetic acid diesters 2. Allylic fluoroaconitates 3 and their vinylic isomers 4 are Obtained. The amount of 4 decreases if lithium bromide is added to the reaction mixture.     

Synthesis of Organophosphorus Compounds with ‒P˭P≡ and ‒P˭S˭ Units

Abstract

The lithium phosphide tetrahydrofurane complexes 1 react with phosphinic acid chlorides (2) to yield diphosphenes (4), possessing a tri- and a quinquevalent phosphorus atom; the diphosphane oxides 3 are regarded to be intermediate steps of the transformation.     

An Expeditious Route to Monoprotected α-Keto Aldehydes with Control of Regiochemistry

Treatment of representative orthoesters (2) with pyruvonitrile (3) afforded the corresponding α, α-diethoxynitriles (4) in 65–80% yields. Subsequent reduction of the latter using lithium aluminum hydride, followed by careful hydrolysis of the aldimine intermediates, led to the procurement of α, α-dialkoxy aldehydes (5) in 80–90% yield.     

Base Promoted Rearrangement of Carbonate Esters Derived from Aldehyde Cyanohydrins: Application to the Synthesis of α-Keto Esters

Acylation of the cyanohydrin derivative (2) of representative aldehydes with ethyl chloroformate, followed by treatment of the corresponding mixed carbonate esters (3) with lithium hexamethyldisilazide, afforded the cyanohydrin derivative (4) of α-keto esters. Cleavage of the latter (4) with 2,6-lutidine in the presence of silver nitrate led to the procurement of α-keto esters in >50% overall yield.     

Organometallic ionophore for alkali metal cations

Complexes of a novel synthetic organometallic ionophore with lithium and sodium cations have been characterized by single-crystal X-ray diffraction. The crystal structure of the lithium complex consists of cation-liganddimers with a tetrahedral coordination around Li. The sodium complex reveals a different structure type consisting of cation-ligandtrimers, with water molecules being included between the trimeric entities. The coordination sphere around the Na ions has a distorted octahedral symmetry. It is anticipated that the observed structures of dinuclear Li and trinuclear Na complexes represent possible modes of aggregation of the cation-ligand entities in lipophilic media.     

Synthesis of an Optically Active Trisubstituted α,β-Butenolide, (S)-4, 6-Dihydroxy-2, 3-dimethyl-2-hexesoic Acid 1, 4-Lactone,from 2-Deoxy-D-ribose

The title compound has been synthesized efficiently from 2-deoxy-D-ribose. The synthesis involves : 1) an aldol like carbon-carbcr. bond formation of (S)-3, 5-dibenzyioxy-2-pentanor.e (8) with a lithium enolate of methyl propanoate, and 2) O-de-benzylation of the aldol adducts (11) for a γ-lactonization followed by β-elimination of the desired butenolide skeleton.     

Reactions of Difluorophosphoranes and P-Fluoro Ylids

Abstract

MePF₂ (NMe₂)2 (1) reacts with n-butyl lithium in a molar ratio₂ to the methylenediaminophosphorane 1 (2) and in a ratio of 1:2 to a diphosphete 2 (3). Silylsubstituted alkylidenefluorophosphoranes could be prepared from 1 and on silicon chloro compounds (2).     

The Synthesis of Hydronaphthalenes from m-Toluic Acid via Cyclization of Thioacetal Monosulfoxides

We recently developed a convenient route to hexahydronaphthalenols such as 5 (R=CO₂CH₃ or CH₃) starting from m-toluic acid (1)¹. The key features of the route involved reduction-alkylation of the toluic acid to the dihydro derivative 2 ², subsequent deprotection and oxidation of the side chain primary alcohol, and acid-catalyzed cyclization of the resulting aldehyde 4. In the case of the dimethylnaphthalenols 5 (R=CH₃), conversion of the angular carboxylic function to the methyl group was effected prior to cyclization via reduction of the p-toluenesulfonic ester of the neopentyl alcohol 3 (R=CH₂OH) using lithium triethylborohydride³.     

An Improved Synthesis of Hexamethylphenalene

The synthesis of 1,3,4,6,7,9-hexamethylphenalene (2) has been improved from 15 steps to a four step procedure. The overall yield has been increased from an estimated 5% to 45%. Key steps in the synthesis are the reaction of 3,5-dimethylbenzylmagnesium chloride with 2,4-pentanedionato lithium in THF to make 5-(3,5-dimethyl-phenyl)-4-methyl-4-hydroxy-2-pentanone (5) and the Lewis acid acylation-alkation of 1,3,6,8-tetramethylnaphthalene using 3-chlorobutanoic chloride in hexane with sonication to make 1,3,4,6,7,9-hexamethyl-phenalane (2).     

A Novel Approach to the Synthesis of C-Glycosyl Compounds: The Wittig Rearrangement

Abstract

Partially protected benzyl α-and β-pyranosides undergo Wittig rearrangement reactions on treatment with strong bases in tetrahydrofuran to give hydroxymethylphenyl C-glycosyl derivatives. Two products were generally obtained and all Wittig rearrangement products retained the configuration at the migrating anomeric center. In benzene, benzyl 4,6-O-isopropylidene-β-D-glucopyranoside reacted with n-butyl lithium to give addition to the anomeric center accompanied by ring opening with loss of the aglycone. Allyl glycosides do not give Wittig rearrangement products.     

Diselenide-assisted sulfuration of dienes

Various diselenides assist in the sulfuration of dienes giving cyclic di- and tetrasulfides as main products. The reaction requires a 2-fold excess of diselenides to be efficient. Catalytic amounts of diselenides result in lower yields. This is likely due to secondary reactions (polymerization, aromatization) occurring during extended reaction times under catalytic conditions. It was verified that the sulfur-transferring properties of diselenatetrasulfides are virtually identical to those of diselenides combined with sulfur. Contrary to previous claims, not only the cyclic diselenatetrasulfide but also linear diselenatetrasulfides (RSeS_nSeR) transfer sulfur to dienes. A mechanism is proposed and its implications to the nature of diatomic sulfur are discussed.     

Methyl 2,6-Dideoxy-4-α-Methyl-α-D-Arabino-Hexopyranoside

Abstract

Synthesis of methyl 2,6-dideoxy-4-O-methyl-α-D-arabino-hexopyranoside (2) has been accomplished starting from readily available methyl 2-deoxy-α-D-arabino-hexopyranoside (3). The derived 4,6-dimesylate derivative 7 was simultaneously deoxygenated and hydrolysed at C-6 and C-4 with lithium aiuminatm hydride in refluxing tetrahydrofuran. subsequent methyíaíion and debenzy[icaron]ation of 8 gave the title product.     

1,4,7,10-Tetraoxacyclododecane(12-Crown-4) as Neutral Carrier for Lithium Ion in Lithium Ion Selective Electrode

Abstract

1,4,7,10-Tetraoxacyclododecane (12-crown-4) (I) and its lithium complex (II) are used as neutral carriers for lithium ion in polyvinylchloride membrane ion selective electrodes. The lithium response varies with concentration, being near Mernstian at low (10^?5-10^?4 M) concentrations and sub-Nernstian (24-28 aV) at higher concentrations (10^?3 M). The selectivity coefficients K_Li ^Pot _M for II are: Na⁺ (0.12), K⁺ (0.66), Cs⁺ (0.15), Mg²⁺ (1.6 × 10^?4), Ca²⁺ (3.1 × 10^?4), Ba²⁺ (9.5 × 10^?7), NH⁺ ₄ (9.0 × 10^?2), H⁺ (2.2).     

A Stereooontrolled Approach to Tri and Tetrasubstttuted Cyclohexanones

A series of reactions utilizing acetals 2–5 with organo cuprates was studied to determine the stereoselectivity of the 1,4-conjugate addition. A90:10 stereoselectivity was observed from the reaction of lithium or bromomagnesium divinyl cuprate with acetal 5 which generated a facile entry to the tetrasubstituted cyclohexanone via a consecutive 1,4-conjugate addition - 1,3-alkylation sequence.     

An Efficient and Unambiguous Synthesis of 2-Hydroxymethyl-1, 3-Propanediol

In 1949, Fujui³ reported the synthesis of what was presumed to be 2-hydroxymethyl-1, 3-propanediol (4) in 70% yield by the condensation of acetaldehyde with formaldehyde (1:2.5 molar ratio) in the presence of calcium hydroxide, and subsequent catalytic hydrogenation over a nickel catalyst. The product was reported to have a melting point of 182°. In 1955, the triester tris-(carbethoxy) methane (5) was reduced with lithium aluminum hydride to give a product with a reported melting point of 58–62°; the yield was only 5%.⁴ Owing to the conflicting data in the literature and the vast potential of 4; we have developed an efficient and unambiguous route to 4; this scheme is also adaptable to clean conversions to mono-, di- and tri-O-substituted derivatives of 4:     

Visible light-promoted,iodine-catalyzed selenoalkoxylation of olefins with diselenides and alcohols in the presence of hydrogen peroxide/air oxidant: an efficient access to <Emphasis Type="Italic">α</Emphasis>-alkoxyl selenides

Under iodine-catalyzed and visible light-irradiated aerobic conditions, selenoalkoxylation of olefins with diselenides and alcohols can be efficiently achieved to afford the useful α-alkoxyl selenides in the presence of only 0.5 equiv. of H₂O₂. Controlling the sub-stoichiometric H₂O₂ amount is crucial to avoid the non-selective over-oxidation of the diselenides that leads to the ineffective hyper-valent selenium compounds. Meanwhile, under visible light irradiation, the green, safe, and low-cost air can work as a supplemental mild oxidant in the reaction to ensure selective oxidation of the diselenides, full conversion of the reactants, and ultimately good yield of the products.     

Synthesis of a Selenium-Substituted Diselenide

Abstract

A wide range of diselenides as precursors for selenium electrophiles is already known, but the development of reagents with higher selectivity is still ongoing. Herein we report the first synthesis of selenium-stabilized diselenides together with some preliminary reactions of these reagents in stereoselective selenenylation reactions.     

Synthesis Of 3-(Endo)-[3′Methyl-2′-Buienylsulfonyl]-Camphor by Reaction of the Camphor Enolate with Sulfur Dioxide

The lithium enolate of (+)-camphor reacts with sulfur dioxide and 3-methyl-2-butenyl bromide to produce the β-keto-sulfone 3-(endo)-[3′-methyl-2′-butenyl-sulfonyl]-camphor 4.     

Organic Diselenides and Ditellurides: Disproportionations,Synthesis of Stannyl Selenides,Reactions with Acetylenes

The disproportionation reaction of organic diselenides 1 and ditellurides 2, the synthesis of stannyl selenides 4, and the addition reaction (palladium-catalyzed, thermal) of dialkyl diselenides to acetylenes are discussed.     

Synthesis and Structure–Activity Correlation Studies of Secondary‐ and Tertiary‐Amine‐Based Glutathione Peroxidase Mimics

In this study, a series of secondary‐ and tertiary‐amino‐substituted diaryl diselenides were synthesized and studied for their glutathione peroxidase (GPx) like antioxidant activities with H₂O₂, cumene hydroperoxide, or tBuOOH as substrates and with PhSH or glutathione (GSH) as thiol cosubstrates. This study reveals that replacement of the tert‐amino groups in benzylamine‐based diselenides by sec‐amino moieties drastically enhances the catalytic activities in both the aromatic thiol (PhSH) and GSH assay systems. Particularly, the N‐propyl‐ and N‐isopropylamino‐substituted diselenides are 8–18 times more active than the corresponding N,N‐dipropyl‐ and N,N‐diisopropylamine‐based compounds in all three peroxide systems when GSH is used as the thiol cosubstrate. Although the catalytic mechanism of sec‐amino‐substituted diselenides is similar to that of the tert‐amine‐based compounds, differences in the stability and reactivity of some of the key intermediates account for the differences in the GPx‐like activities. It is observed that the sec‐amino groups are better than the tert‐amino moieties for generating the catalytically active selenols. This is due to the absence of any significant thiol‐exchange reactions in the selenenyl sulfides derived from sec‐amine‐based diselenides. Furthermore, the seleninic acids (RSeO₂H) derived from the sec‐amine‐based compounds are more stable toward further reactions with peroxides than their tert‐amine‐based analogues.