Alkylation of Pyrimidine Derivatives with Chloroacetic Acid Esters

Alkylation of 6-methyluracil, 5-hydroxy-6-methyluracil, and 6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-ylammonium sulfate with isopropyl and ethyl chloroacetates afforded previously unknown alkyl 2-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)acetates, alkyl 2-(1-alkoxycarbonylmethyl-6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-3-yl)acetates, 1,3-bis(alkoxycarbonylmethyl)-6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-ylammonium sulfates, and alkyl 2-[1,3-bis(alkoxycarbonylmethyl)-6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yloxy]acetates.     

Preparation of N-protected allylic amines and α-methylene-β-amino acids from vinylalumination/Baylis-Hillman products via tandem SN2′ substitution-Overman rearrangement

S_N2′ reaction on the acetates obtained from vinylalumination or Baylis-Hillman products, followed by in situ reduction afforded allylic alcohols. Upon conversion to trichloroacetimidates and [3,3]-sigmatropic rearrangement, the corresponding N-protected β-substituted allylic amines were obtained in good yields. Utilization of hydroxy group as the nucleophile furnished allylic hydroxy esters, which were converted to protected α-methylene-β-amino acids via Overman rearrangement.     

Palladium-Catalyzed ‘Metallo-Ene’-Type Cyclization/Vinylstannane Coupling of 1-Acetoxy-octa-2,7-dienes and 1-Acetoxy-oct-2-en-7-ynes

Palladiumbis(dibenzylideneacetone)/tri(2-furyl)phosphine-catalyzed cyclizations of dienyl acetates 2 in the presence of an (1-alkenyl)(tributyl)stannane and ZnCl₂ provided trans-substituted 3-alkenyl-4-vinylcyclopentanes 11 in good yields. Analogous intramolecular carbometallation/C,C-coupling of enynyl acetates 4 , 6 , and 8 furnished, stereospecifically, monocylic trienes 19 , 20 , and 21 , respectively.     

Catalytic aerobic oxidation of substituted 8-methylquinolines in Pd(II)-2,6-pyridinedicarboxylic acid systems

The ability of Pd(II) complexes derived from 2,6-pyridinedicarboxylic acids to catalyze homogeneous regioselective aerobic oxidation of 5- and 6-substituted 8-methylquinolines in AcOH-Ac(2)O solution to produce corresponding 8-quinolylmethyl acetates in high yield was demonstrated; corresponding 8-quinoline carboxylic acids are minor reaction products.     

Palladium-catalyzed asymmetric synthesis of axially chiral molecules

The asymmetric synthesis of chiral 3-alkylidene bicyclo[3.3.0]octane and 4-substituted 1-alkylidene cyclohexane systems has been carried out (in up to 40% ee) by the palladium-catalyzed reaction of allylic acetates with sodium dimethyl malonate or morpholine.     

Preparation of highly branched poly(vinyl acetate) by transfer to allylic carbonate comonomers

Copolymerization of vinyl acetate with allyl carbonates that contain isopropyl groups yields highly branched poly(vinyl acetates).     

Asymmetric hydrogenation of itaconic acid and enol acetate derivatives with the Rh-TangPhos catalyst

[reaction: see text] The Rh-TangPhos catalyst has been used for asymmetric hydrogenation of itaconic acid and enol acetate derivatives. A variety of chiral 2-substituted succinic acids and chiral acetates have been obtained in excellent ee values (up to 99% ee).     

2-(1-Azulyl)ethyl tosylate methylene scrambling in the gas phase. Similarities to solution chemistry

The methylene groups in 2-(1-azulyl)ethyl tosylate are largely scrambled prior to formation of fragment ions in the mass spectrometer. This process also occurs in the 3-nitro analog, where it is dependent on sample residence time in the source and independent of electron energy. It could not be observed with the isomeric 6-substituted tosylates, the 1-substituted acetates or alcohols, or with 2-(p-anisyl)ethyl tosylate. Scrambling occurs in the neutral molecule prior to ionization and a mechanism involving absorption onto the metal surface and formation of a complexed ethylenazulonium ion is suggested.     

Synthesis of 1,2,4-oxadiazines and their rearrangement to pyrimidines

Several amide oximes underwent condensation reactions with dimethyl acetylene dicarboxylate to afford 1:1 adducts. Under basic conditions, these adducts underwent ring closure to afford several methyl [3-(substituted)-4,5-dihydro-5-oxo-6H-1,2,4-oxadiazin-6-ylidene]acetates. The reactions of these compounds with a variety of amines resulted in addition-rearrangement reactions with the formation of the corresponding methyl 2-substituted-5-substituted amino-1,6-dihydro-6-oxo-4-pyrimidine carboxylates.     

Syntheses and spectral characteristics of 6-mono-, 3,6-di- and 3,5,6-trisubstituted-1,2,4-triazines

The reaction of acidhydrazides with α-substituted carbonyl compounds in the presence of metal acetates gives substituted 1,2,4-triazines. These cyclisations could be effected without any added acetate by refluxing in dimethyl formamide, pyridine/acetic acid or dimethyl sulfoxide Sixty five 3,5,6-tri-3,6-di and 6 monosubstituted-1,2,4-triazines (in 50–90% yields) with a wide variation in the C₃ substituent (alkyl, aryl or heteryl) and the C₆-substituent (aryl or heteryl) are reported. The mechanistic path followed in the formation of these compounds is discussed.     

Diastereoselective propargylations with planar chiral chromiumcarbonyl arene complex substituted propargyl cations

The ionization of planar chiral ortho-substituted (arene)Cr(CO)(3)-substituted alpha-propargylic acetates 3 with Lewis acids results in the formation of stable (arene)Cr(CO)(3)-substituted alpha-propargyl cations 4. Subsequent additions of sulfur, nitrogen, oxygen, and pi-carbon nucleophiles to these organometallic electrophiles give rise to the regio- and highly diastereoselective formation of propargyl derivatives 5 in good yields (44-90%; dr = 70:30 to >99:1). The relative stereochemistry of the propargyl acetates 3 and the trapping products 5 was established by several crystal structure analyses, indicating that the cationic propargylations occurred under retention of configuration at the propargylic center. Most important for the diastereoselectivity of the nucleophilic trapping reaction is the configurational stability of the diastereotopic cation 4 as reflected by substituent effects. In situ ionizations according to an S(N)1-mechanism not only result in a considerable loss but also in an inversion of diastereoselectivity.     

亚甲胺叶立德参与的不对称1,3-偶极环加成构建含连续季碳中心的螺四氢吡咯衍生物

Cu(I)催化的亚甲胺叶立德和亚环丙基乙酸乙酯参与的不对称endo-1,3-偶极环加成反应,高效构建了多官能化、含有多个连续季碳中心的5-氮杂-[2,4]庚烷化合物.此反应具有广泛的底物适用性,α-取代的和α-非取代的亚甲胺叶立德和亚环丙基乙酸乙酯都能很好的参与反应,并以很高的产率、优秀的非对映选择性(95:5–98:2 d.r)和对映选择性(87%–98%ee)生成相应的在2,3,4位上含有连续季碳中心的螺四氢吡咯化合物.     

Synthesis of 1,5-diisopropyl substituted 6-oxoverdazyls

1,5-Diisopropyl-6-oxo-verdazyl free radicals were synthesized via the condensation of BOC protected isopropyl hydrazine with phosgene, deprotection with aqueous HCl, condensation with aldehydes to form tetrazanes and finally oxidation to give the free radicals. The introduction of isopropyl groups results in free radicals that show greater solubility in a variety of solvents and are more stable than their methyl substituted counterparts. ESR shows reduced hyperfine coupling to the isopropyl methine hydrogens consistent with this hydrogen being in the plane of the verdazyl ring.     

Convenient synthesis of Z-monoacetates of 2-alkylidene-1,3-propanediols

Various kinds of 3-substituted (Z)-hydroxymethyl-2-propenyl acetates were conveniently obtained in excellent yields by highly regioselective hydrolysis of 2-alkylidene-1,3-propylene diacetates in the presence of 100 w/w % of porcine pancreas lipase (PPL) Type II.     

Palladium(II) catalyzed allylic rearrangement: Stereoselective synthesis of 2-substituted (e)-β acetoxy (or benzoyloxy)ethylidenecyclohexanes

Diastereomeric mixtures of 2-substituted 1-vinyclyclohexyl acetates (or benzoates) are rearranged stereoselectively to 2-substituted (E)-β-acetoxy(or benzoyloxy)ethylidenecyclohexanes by the catalysis of bis(acetonitrile)palladium(II) chloride. A mechanism related to the stereoselectivity and reactivity is discussed in terms of the conformational requirements in a transition state.     

Synthesis of 3-substituted quinolines via transition-metal-catalyzed reductive cyclization of o-nitro Baylis-Hillman acetates

Reductive cyclization of o-nitro-substituted Baylis-Hillman acetates by carbon monoxide, catalyzed by [CpFe(CO)(2)](2), gives moderate to good yields of 3-substituted quinolines.     

Trimethylsilyl tetrafluoroborate a convenient reagent for solvolysis reactions

Conversions of cyclopropyl carbinols (or their acetates) and ketones into homoallyl and γ-substituted ketone derivatives, respectively, are accomplished by trimethylsilyl tetrafluoroborate efficiently and under mild conditions.     

Palladium-catalyzed allylation of lithium 3-alkenyl-1-cyclopentenolates-triethylborane and its application to a selective synthesis of methyl (z)-jasmonate1

A Pd-catalyzed allylation of 3-substituted 1-cyclopentenolates with readily obtainable and storable γ-monosubstituted (Z)-allylic acetates in a 1:1 ratio in the presence of 2 mol % of Pd(PPh₃)₄ featuring high yields and high stereo- and regioselectivities has been developed and applied to the synthesis of methyl (Z)-jasmonate.     

High enantioselectivity in rhodium-catalyzed allylic alkylation of 1-substituted 2-propenyl acetates

[reaction: see text] Rhodium-catalyzed asymmetric allylic alkylation of 1-substituted 2-propenyl acetates with dimethyl malonate proceeded with high enantioselectivity in the presence of cesium carbonate as a base and a rhodium catalyst generated from Rh(dpm)(C(2)H(4))(2) (dpm = dipivaloylmethanato) and a chiral phosphino-oxazoline whose basic skeleton is axially chiral binaphthyl to give branch alkylation products in greater than 90% ee.     

Synthesis of 2-substituted 1,3-butadienyl compounds by palladium-catalyzed regioselective 1,2-elimination reaction of methylvinylcarbinol acetates

Alkylation of the dianion of 3-methyl-3-buten-2-ol, followed by acetylation and palladium-catalyzed 1,2-elimination reaction of the so obtained methylvinylcarbinol acetates allows to synthesize regioselectively 2-substituted 1,3-butadienyl compounds having high isomeric purity.