2,5-Bis-(butyltelluro) thiophene as a convenient precursor for the synthesis of 2,5-bis-(acetylenic) thiophenes

Both symmetrically and unsymmetrically substituted 2,5-bis-(acetylenic) thiophene derivatives were obtained in good yields under mild conditions through palladium-catalyzed cross coupling reaction of 2,5-bis-(butyltelluro) thiophene 2 and terminal alkynes. The methodology represents a general and efficient protocol for carrying out the synthesis of thiophene derivatives with potential biological activities.     

A convenient stereoselective synthesis of a (−)-vertinolide precursor

A short practical method for the enantioselective synthesis of (−)-vertinolide precursor 2 is described. The readily available chiral β-alkoxy substituted acrylate 7 has been reacted with the ethyl levulinate to form the tetronic acid nucleus 8, which in three subsequent steps was converted to the known precursor 2 in high overall yield.     

An economical and convenient preparation of 2-(phenylthio)cyclobutanone,a synthetic equivalent of cyclobutanone

A practical procedure is given for the preparation of 2-(phenylthio)cyclobutanone ($\text{3}$) and the use of the latter as a convenient substitute for cyclobutanone is demonstrated.     

Triallyl(aryl)silanes serve as a convenient agent for silicon-based cross-coupling reaction of aryl halides

Triallyl(aryl)silanes, stable and easily accessible arylsilanes, were found to react with aryl bromides in the presence of a palladium catalyst (PdCl₂-PCy₃) and tetrabutylammonium fluoride (TBAF) in good yields. The scope of the reaction is broad, and a wide variety of functional groups are tolerant. Allyl groups on Si are readily cleaved upon treatment with TBAF to form fluorosilanes, silanepolyols, siloxanes and/or their mixed forms, which might be responsible for high efficiency of the reaction.     

Bis(acetylacetonato)tricarbonyl tungsten(II): a convenient precursor to chiral bis(acac) tungsten(II) complexes

Two equivalents of acetylacetonate (acac) have been successfully introduced into a monomeric tungsten(II) coordination sphere. With the tetracarbonyltriiodotungsten(II) anion as a precursor, the formation of a tungsten(II) bis(acac) tricarbonyl complex, W(CO)3(acac)2, 1, has been accomplished. The addition of PMe3 or PMe2Ph to tricarbonyl complex 1 formed tungsten(II)bis(acac)dicarbonylphosphine complexes 2a and 2b, respectively. Single-crystal X-ray diffraction studies of the parent tricarbonyl complex, 1, and dicarbonyl trimethylphosphine complex 2a confirmed seven-coordinate geometries for both complexes. Variable-temperature 1H and 13C{1H} NMR spectroscopy revealed fluxional behavior for these seven-coordinate molecules: rapid exchange of the three carbon monoxide ligands in 1 was observed, and movement of the phosphine ligand through a mirror plane in a C(S) intermediate species was observed for both 2a and 2b. Tricarbonyl complex 1 reacted readily with alkyne reagents to form bis(acac)monocarbonylmonoalkynetungsten(II) complexes 3a (PhC(triple bond)CH) and 3b (MeC(triple bond)CMe). Variable-temperature 1H NMR spectroscopy was used to probe rotation of the alkyne ligand in 3a and 3b. The introduction of two alkyne ligands was accomplished thermally using excess PhC(triple bond)CPh to form bis(alkyne) complex 4 which was characterized crystallographically, as well as by 1H and 13C NMR spectroscopy. The availability of W(CO)3(acac)2 as a source of the W(acac)2 d4 moiety lies at the heart of the chemistry reported here.     

An unusual reaction of 1,1-dicyano-2,2-bis(trifluoromethyl)ethylene

Translated from Izvestiya Akademii Nauk SSSR, Seriya KMmicheskaya, No. 6, pp. 1451–1452, June, 1988.     

Synthesis of (-)-pinolidoxin: divergent synthetic strategy exploiting a common silacyclic precursor

[reaction: see text] We describe a highly convergent and efficient synthesis of (-)-pinolidoxin, a potent modulator of plant pathogenesis, providing unambiguous determination of the relative and absolute stereostructure of this highly oxygenated fungal metabolite. Our unique strategy highlights the applications of novel silacyclic precursors for stereocontrolled polyol synthesis and features the finding of the reversible ring-closing metathesis.     

A convenient asymmetric synthesis of a beta-amino ester with additional functionalization as a precursor for peptide nucleic acid (PNA) monomers

We report the asymmetric synthesis of di-3-pentyl (3S,alphaS,7E)-3-N-benzyl-N-alpha-methylbenzylamino-dec-7-enedioate (9), which contains the correct functionalization to produce delta-amino acid derivatives to be used as monomers for Peptide Nucleic Acid (PNA) formation With this aim, thymine-pentanoic acid 15 and some of its ester derivatives were obtained, their reactivity was studied and the noteworthy ethyl ester 12 was quantitatively produced by transesterification of methyl ester 11, thus paving the way for the synthesis of the thymine-containing amino ester IV, which has been designed as a building block for a Nucleic-Acid analog with a chiral, flexible peptide backbone.     

Vinylmetallics as ligands III. Synthesis and characterization of potassium trichloro(trimethylvinylsilane)platinate(II)

The preparation and some reactions of the compound potassium trichloro(trimethylvinylsilane)platinate(II) are reported.     

A convenient synthesis of new (1,2,4-triazolylamino)pyrimidines from cyanamide precursor

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Highly selective synthesis of 1-(silyl)-1-(boryl)ethenes via a ruthenium-catalyzed silylative coupling reaction

An efficient silylative coupling of trisubstituted vinylsilanes with dialkoxy(vinyl)boranes is described. Under optimum conditions the reaction offers a selective route to 1-(silyl)-1-(boryl)ethenes, which are potentially attractive intermediates in organic synthesis     

An unusual example of a 1,1-cycloaddition reaction of a diazoalkane

Thermolysis of the sodium salt of E-1,4-diphenyl-3-buten-1-one N-tosylhydrazone gave rise to the corresponding diazoalkane which undergoes a subsequent 1,1-cycloaddition reaction to produce 3,6-diphenyl-1,2-diazabicyclo[3.1.0]hex-2-ene.     

An unusual, mild and convenient one-pot two-step access to (E)-stilbenes from hydroxy-substituted benzaldehydes and phenylacetic acids under microwave activation: a new facet of the classical Perkin reaction

A mild and convenient one-pot two-step synthesis of hydroxystilbenes with trans selectivity has been developed through a modified Perkin reaction between benzaldehydes and phenylacetic acids bearing 4- or 2-hydroxy substitution at the aromatic ring, in the presence of piperidine-methylimidazole and polyethylene glycol under microwave irradiation. The observation of a simultaneous condensation-decarboxylation leading to the unusual formation of hydroxystilbenes in lieu of α-phenylcinnamic acid reveals an interesting facet to the classical Perkin reaction. The developed protocol provides a green alternative to the prevalent methods employing a toxic decarboxylating agent in the form of quinoline/Cu salt, and the requirement for harsh protection-deprotection steps for the synthesis of hydroxylated stilbenes.     

An unusual reaction product from a 1,3-diborolene and tetracarbonylnickel. Structure of a bis(allyl)nickel complex

The bis(allyl)nickel complex (η³-3-vinyl-2,4,5,6-tetraethyl-1-oxa-2,6-diboracyclohexenyl)(η³-2,3,4,5,6-pentaethyl-1-oxa-2,6-diboracyclohexenyl)nickel(IV) is formed by initial insertion of CO from Ni(CO)₄ into the five-membered 1,3-diborolene I, to give a six-membered ring. Subsequent exchange of the CHCH₃ group of I for the oxygen atom of the inserted CO and migration of a hydrogen atom from the

group of one ring to that of the other results in formation of the bis[1-oxa-2,6-diboracyclohexenyl]nickel, IV, having one vinyl and nine ethyl substituents. An X-ray structural analysis of IV shows the non-planarity of the C₃B₂O rings; the boron and oxygen atoms lie 0.4 and 0.7 Å, respectively, away from the best plane through the allyl carbon atoms. IV crystallizes in the space group P2₁/n with a = 9.065(2), b = 16.264(3), c = 10.187(2) Å, β = 104.28(1)°, and Z = 2.     

Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione: An unusual long-lived triplet as a reaction intermediate

Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione (DBD) is presumed to involve a short-lived carbene, followed by Wolff rearrangement to a long-lived ketene. We have detected ketene ylides following photolysis of DBD in the presence of amines but not with pyridine. The triplet state of DBD lives several microseconds, an unusual observation for a diazo compound; however, the triplet is not a ketene precursor, which must result from excited singlet state fragmentation of DBD.     

Pyrazoline derivatives: A convenient synthetic route to new pyrazolo-benzothia-(oxa) or diazepinone derivatives

New pyrazolo-[3,4-b]-[1,5]-benzoazepinone derivatives are reported. One pot reactions of 5-chloro-4-carboxy-1-phenyl (3-substituted) pyrazole derivatives with o-thioaminophenol, o-phenylenediamine, and o-aminophenol derivatives were realized. The influences of the polarizability of the heteroatoms on the reaction rates and chemical yields are discussed. © John Wiley & Sons, Inc.