Presence Of BuLi Research Articles

ChemInform Abstract: Syntheses of Functionalized Allylamines via Lithiated Intermediates.

AbstractVinyltributylstannane (I) is alkylated by aldehydes, ketones, and cyclohexenone in the presence of BuLi.

Convergent Total Synthesis of (+)‐Mycalamide A.

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Convergent Total Synthesis of (+)-Mycalamide A

The details of a convergent total synthesis of (+)-mycalamide A are described. Yb(OTf)3-TMSCl-catalyzed cross-aldol reaction conditions are used to synthesize the right segment of mycalamide A. In this reaction, an acid-sensitive aldehyde reacts with methyl trimethylsilyl dimethylketene acetal without epimerization to provide the desired aldol adduct. Additionally, a tetrahydropyran ring, which is the left segment of mycalamide A, is prepared using a novel one-pot delta-lactone formation methodology. Both segments are constructed from a common starting material, d-mannitol. These segments are then coupled in the presence of BuLi, and the functional groups are transformed to complete the synthesis of (+)-mycalamide A.

Synthesis of the Antibiotic (R)‐Reutericyclin via Dieckmann Condensation

Abstract(R)‐Reutericyclin ((R)‐1), a bactericidal, amphiphilic natural product with a trisubstituted tetramic acid moiety, was prepared in four steps from D‐leucine in an overall yield of 24%. The chiral heterocyclic portion of 1 was synthesized by Dieckmann cyclization of ethyl N‐(acetoacetyl)leucinate (7), and the resulting pyrrole derivative 8 was N‐acylated with (E)‐dec‐2‐enoyl chloride in the presence of BuLi at − 70° (Scheme 2). This new procedure is straightforward and allows the synthesis of both antipodes of reutericyclin in an enantiomeric excess (ee) of ca. 80%.

Unexpected formation of new chiral 3-amino-5-alkyl-2,5-dihydro-1 H-pyrrolin-2-ones from N-Boc-α-amino esters

We describe a one-pot process involving the DiBAl-H reduction of the ester moiety of N-protected α-amino esters, followed by Horner–Wadsworth–Emmons olefination in the presence of the trimethyl ester phosphonoglycinate carbanion allowing the formation of new chiral 3-amino-5-alkyl-2,5-dihydro-1 H pyrrolin-2-one 5 . The Z-enoate 4b , which is formed during this reaction, could be converted into the corresponding lactam 5b under UV irradiation with the presence of BuLi.

Properties and Reactions of Substituted 1,2‐Thiazetidine 1,1‐Dioxides: Functionalization and Reactions at C(4) of the β‐Sultam

AbstractThe introduction of functional groups at the 4‐position of the β‐sultam ring was realized by the synthesis of mono‐ and disubstituted derivatives by reactions of N‐silylated β‐sultams with electrophiles in the presence of BuLi or LDA. As electrophiles, ketones, chlorosilanes, a β‐sultam, CO2, chloroformiate, halogen, azodicarboxylate, phenyltriazoledione, tosyl azide, 1,3,5‐triazine, propyl nitrate, and phenyl isocyanate were used. Furthermore, a number of derivatives of these substitution products were synthesized. All products were characterized by standard spectroscopic methods, and conformations were studied, supported by calculation.

SCOOPY-Reaktionen: Die Regioselektivität der Alkenol-Synthese

Ph3P+CH2R (R = H, Me) reacted with aldehydes R1CHO (R1 = n-C5H11, Me2PrC, Ph) in the presence of BuLi and HCHO to give primary alkenols R1CH:CRCH2OH; ketones R2R3CO [R2, R3 = Me, Ph or (CH2)4, (CH2)5] and spatially crowded aldehydes gave secondary and tertiary alcs. R2R3C(OH)CR:CH2. A b-oxido phosphonium ylide was a reaction intermediate. [on SciFinder (R)]

Synteza i wlasciwosci polifenylenow

A review with 36 refs, covering the synthesis routes to polyphenylenes, e.g., the Friedel-Crafts reactions, oxidative cationic polymerization of benzene in the presence of AlCl 3 /CuCl 2 , anionic polymerization in the presence of BuLi, the Yamamoto reaction, Diels-Alder reactions, etc. The products show broad MWD, various isomeric forms, colors, etc. Physicochemical properties (crystallinity, solubility, thermal resistance, electric conductivity) are described in relation to chemical structure. Service properties of construction materials (pump and mixer parts, anticorrosive and ablative coatings) produced from poly(p-phenylene)s (I) are also characterized. As the chain length is increased, the solubility and the melting temperature of linear I decreases and increases, resp. Conventional processing procedures are inapplicable to I. Powdered I compacted at 520 MPa at room temperature and sintered in nitrogen at 500°C and 140 MPa for 1 h, yielded a product resistant to high-T hydrolysis and chemical agents. Polycondensation (300°C) of terphenyl with m-benzene disulfone chloride afforded soluble oligo(phenylene)s; these dissolved in organic solvents serve as adhesives in the production of laminates. Extremely pure I is applied as a (semi)conductor.

Annulation of 3-[(R)-p-Toluenesulfinyl]-2-oxopropylidenetriphenyl-phosphorane with 1,4-Enediones; Highly Enantioselective Synthesis of Cyclopentenones

3-[(R)-p-Toluenesulfinyl]-2-oxopropylidenetriphenyl-phosphorane reacted with 1,4-enediones in the presence of BuLi to give (4S,5R)-4-acylmethyl-5-[(R)-p-toluenesulfinylcyclopent-2-enones in a highly diastereoselective fashion. Subsequent desulfurization of the cyclization products furnished highly enantiomerically enriched (S)-4-acylmethylcyclopent-2-enones.

Structures and Reactions of Alkoxymethyl(alkali metals). Ethylation by Methyl Ethers in the Presence of Organometallic Bases

Abstract Structures and reactions of CH3OCH2M (M = Li, Na, K) were investigated in a theoretical manner. CH3OCH2M has the acute bond angle of ∠M-C-O due to a strong coordination of the oxygen to the alkali metals. The nucleophilic substitution reaction of the substrate CH3OCH2Li by the nucleophile CH3OCH2Li is more preferred than the carbene generation by α-elimination and a nucleophilic substitution of CH3OCH2Li by CH3Li. The resulting 2-methoxyethyllithium readily liberated lithium methoxide to afford ethylene, which added to the anion species to give an ethylated product. Among the CH3OCH2M (M = Li, Na, K), CH3OCH2K is the most nucleophilic, due to the high σC–K level, while CH3OCH2Li is the most nucleophilic because of the lowest σ*C–O level. This supports a previously proposed mechanism for the ethylation of indole derivatives by methyl ethers in the presence of BuLi - t-BuOK.

Vinylsilanes as Monomers for Side Chain Polymer Liquid Crystals

A series of novel side chain polymers−silylated polyethylenes were prepared containing 4‘-methoxyphenyl-4-(ω-alkenyloxy)benzoate mesogenic groups of the general formula {−CH2−CH[SiMe2(CH2)mOC6H4C(O)OC6H4OMe]}n−, where m = 4, 5, 8, 11. The ones having five and eight carbon atoms in the alkane moiety of a flexible spacer proved to be liquid crystalline, independent of molecular weight (DP = 75, 230). Alternative synthetic pathways have been described starting with anionic polymerization of Me3SiVi or Me2PhSiVi in the presence of BuLi, followed by functionalization of side silyl group to give reactive Si−H bonds and hydrosilylation of terminal, mesogenic alkenes. The properties of liquid crystal polyethylenes were compared with those of side chain polycarbosilanes of similar structure. The advantage of polyethylenes, while preserving all important features of polycarbosilanes, is shown by their broad temperature range of mesophase formation and the economically attractive synthesis.

N.C.A. 11C-labelling of benzenoid compounds in ring positions: synthesis of 3-nitro-[3-11C]toluene and 4-nitro-[4-11C]toluene and their corresponding toluidines

The paper describes the syntheses of n.c.a. 3-nitro-[3-11C]toluene (3a) and 4-nitro-[4-11C]toluene (3b) by reaction of nitro-[11C]methane (1) with 5-dimenthylamino-2(or 3)-methyl-penta-2,4-dienylidene-dimethylammonium tetrafluoroborate (2a or 2b) in the presence of BuLi, utilizing the synchronous six-electron cyclization of hexatriene systems into aromatics. Starting from 1, 3a and 3b were prepared in a radiochemical purity of about 87% and 78% and with a mean specific radioactivity of 1 Ci/μmol (37 GBq/μmol) within 10 min. Related to 1, the reproducible radiochemical yields of 3a and 3b (decay-corrected) were 85±5% and 75±5%. Reduction of 3a and 3b by heating the above reaction mixture with aqueous Na2S produced m-[1-11C]toluidine (7a) of a radiochemical purity of about 82% and p-[1-11C]toluidine (7b) of a radiochemical purity of about 68%. The reproducible radiochemical yields of 7a and 7b (decay-corrected) in relation to 1 were 78±5 and 65±5%, the synthesis time from 1 was 21 min and 16 min. © 1998 John Wiley & Sons, Ltd.

Dialkynyl selenides: Synthesis, 13C NMR spectra, and molecular orbital calculations

AbstractReactions of SeCl4 with lithium bis(trimethylsilyl)amide and terminal acetylenes in the presence of BuLi or AIBN afforded the corresponding dialkynyl selenides in moderate to high yields. The reaction may proceed via a selenium amide 7 and an alkynyl selenium amide 8. The comparison of 13C NMR spectra of dialkynyl selenides and tellurides has disclosed that the differences of the chemical shift of acetylenic carbons between Se and Te derivatives are consistent regardless of their substitution patterns. Ab initio molecular orbital calculations are reported for dialkynyl ether and chalcogenides. The calculated structures, charge distributions, and orbital energies are discussed.

Synthese von Triafulven‐Vorstufen aus trisubstituierten Cyclopropanen

Synthesis of Triafulvene‐Precursors from Trisubstituted CyclopropanesTrisubstituted cyclopropanes 5a–f are prepared by carbene addition to the appropriate olefins. While 5a (Y = OAc) and 5c (Y = Cl) rearrange in the presence of BuLi, 5d (Y = SPh) is stable enough to allow the envisaged sequence for triafulvene (Scheme 2) : halogen‐Li exchange, followed by methylation of 6d, gives 7d in a 93% yield; after base‐induced elimination of HBr from 7d, the key precursor 1‐methylene‐2‐(phenylthio)cyclopropane (9, 70% yield) is isolated. Compound 9 is transformed into the corresponding sulfoxide 10 (83%), sulfone 11 (80%), and sulfonium fluoroborate 12 (95% yield) by subsequent oxidation and methylation, respectively. Some 1H‐NMR results of cyclopropanes 5a–f and 7d as well as of methylidene‐cyclopropanes 9–11 are discussed.

Tandem Wittig reactions of 1,1-diphenylphosphorinanium salt

The title cyclic phosphonium salt (1) reacted with various aldehydes to give the phosphine oxides (2a–d) in good yield; these when treated with aldehydes in the presence of BuLi gave the alcohols (4a, b). The alcohol (4a) was easily converted into the 1,6-diene (5) by treatment of NaH in DMF. The stereoselectivities of these reactions are also described.

Thiophilic additions of functionalized carbanions to sulfines

AbstractThe reaction of three types of sulfines with functionalized carbanions is described. Di‐p‐tolylsulfine 1 reacts with excess of MeSOCH2Na at the sulfine sulfur atom (thiophilic addition) to give Tol2CHS(O)CH2SOMe (Tol = p‐MeC6H4). Similarly, acetonitrile with excess of sodium amide adds thiophilically. N,N‐Diethyl χ‐lithio‐n‐butyramide and dilithio‐n‐butyric acid also form thiophilic addition products. Methyl p‐tolyl sulfone in the presence of BuLi and excess of t‐BuOK affords the adduct Tol2CHS(O)CH2SO2Tol, whereas lithiomethyl p‐tolyl sulfone furnishes alkenesulfone Tol2CCHSO2Tol. It is presumed that the primary adduct rearranges via a thiocarbonyl ylide and an episulfide. From α,α‐dilithiobenzyl cyanide Tol2CC(Ph)CN is obtained by a similar rearrangement. α‐Lithioisopropyl p‐tolyl sulfone with sulfine 1 gives the olefin Tol2CCMe2 which arises from a Ramberg‐Bäcklund type rearrangement of the primary thiophilic adduct. Similarly, p‐tolyl(phenylthio)sulfine 2 and p‐tolyl(phenylsulfonyl) sulfine 3 give thiophilic addition products with some of the carbon nucleophiles mentioned above. The mechanism of the thiophilic reaction is discussed.

Reactivite des carbanions benzyliques : VI. Structure et reactivite du trimethylsilyl-9 dihydro-9,10 anthracene; preparation des bis(trimethylsilyl)-9,9 et trimethylsilyl-9 alkyl-9 dihydro-9,10 anthracenes

The structure of 9-trimethylsilyl-9,10-dihydroanthracene (Me 3SiDHA) has been studied by NMR; the coupling constants of the three 9,10 protons do not change at between 25 and 90°C (ABM spectrum; J AB }- 18.2; J AM ⋍ 1.2; J BM ⋍ 0.3 Hz in toluene-d 8), indicating that the Me 3Si group prefers the quasi axial position. In the presence of BuLi in THF, Me 3SiDHA reacts with Me 3SiCl to yield three new products: 9,9-bis(trimethylsilyl)-9,10-dihydroanthracene (IId) (major), (9,10-dihydroanthracen-9-yl)dimethylsilyl(trimethylsilyl)methane (V) and (9-trimethylsilyl-9,10-dihydroanthracen-9-yl)dimethylsilyl(trimethylsilyl)-methane (VI) together with the known 9,10-bis(trimethylsilyl)-9,10-dihydroanthracene ( cis and trans). The carbanion of Me 3SiDHA can also be alkylated (alkyl  Me, Et, i-Pr) to the new 9,9-disubstituted derivatives: 9-Me 3Si-9-alkyl-DHA. The formation of the carbanion of Me 3SiDHA has been investigated and reveals a competition in the abstraction by the base of H 9 and H 10; the latter is less crowded but the 9-carbanion is stabilized by the vicinity of the silicon atom. The carbanion obtained from Me 3SiDHA reacts exclusively at C(9) with D 2O. A study of the alkylation of 9-trimethylsilyl-9-deuterio-9,10-dihydroanthracene shows that the generation of the 10-carbanion is followed by a 1,4 hydrogen rearrangement which yields the 9-carbanion. The mechanism is discussed and the roles of Me 3Si and t-Bu are compared in the DHA series.

Investigation of the optical anisotrophy of solutions of stereospecific polymethylmethacrylate synthesized under different conditions

Using methods of flow birefringence and viscometry a study has been made of the optical anisotropy of solutions of stereospecific PMMA synthesized under different conditions: in presence of BuLi, PhMgBr, PMMA of stereoblock structure prepared in presence of BuLi, as well as PMMA synthesized on BuLi in presence of syndiotactic PMMA. The optical anistropy values of solutions of the PMMA samples examined. and variations in these values with temperature, show that different conditions of stereospecific polymerization of methyl methacrylate lead to the formation of polymers having different intramolecular and supermolecular structures.