Asymmetric [2,3] Wittig rearrangement of crotyl furfuryl ethers

Asymmetric Wittig rearrangement of crotyl furfuryl ethers was investigated in diastereo- and enantioselective manners. Both (2S,3Z)- and (2S,3E)-3-penten-2-yl furfuryl ethers 3 and 9 rearranged with complete chirality transfer to give the syn- and anti-isomers 4 and 10, respectively. Enantioselective Wittig rearrangement of both (Z)-and (E)-crotyl furfuryl ethers 15 and 17 using butyllithium and (−)-sparteine was examined to afford (1S,2R)-1-(2-furyl)-2-methyl-3-buten-ol 16 in up to 43% ee.     

Tandem catalytic allylic amination and [2,3]-Stevens rearrangement of tertiary amines

We have developed a catalytic allylic amination involving tertiary aminoesters and allylcarbonates, which is the first example of the use of tertiary amines as intermolecular nucleophiles in metal-catalyzed allylic substitution chemistry. This process is employed in a tandem ammonium ylide generation/[2,3]-rearrangement reaction, which formally represents a palladium-catalyzed Stevens rearrangement. Low catalyst loadings and mild reaction conditions are compatible with an unprecedented substrate scope for the ammonium ylide functionality, and products are generated in high yields and diastereoselectivities. Mechanistic studies suggested the reversible formation of an ammonium intermediate.     

A practical synthesis of [C4] N-benzylpiperazine from [C2] glycine

A high yielding gram-scale synthesis of [¹³C₄] N-benzylpiperazine for use as a convenient and versatile building block in isotope labeling studies of clinical drug candidates is reported.     

Synthesis of the C17-C25 subunit of lasonolide A utilizing a Tsuchihashi-Yamamoto type rearrangement

An efficient synthesis of the C₁₇-C₂₅ subunit resident in (−)-lasonolide A is reported herein. The key reaction features that were utilized include a Tsuchihashi-Yamamoto type rearrangement and Molander-Reformatsky SmI₂ mediated intramolecular aldol reaction sequence. Lastly, a diastereoselective target oriented β-C-glycoside formation sequence via an oxocarbenium reduction completed the stereochemistry required for the completion of the C₁₇-C₂₅ segment of (−)-lasonolide A.     

On the [2,3] sigmatropic rearrangement of allylic nitro compounds

Allylic nitro compounds undergo relatively clean [2,3] sigmatropic rearrangement upon heating in refluxing 1,2-dichlorobenzene in the presence of DABCO to give the corresponding allylic alcohols via the intermediate allylic nitrite. [reaction: see text]     

A stereoselective synthesis of the C15-C25 subunit of (+)-lasonolide A

The C₁₅-C₂₅ upper THP segment 2 of (+)-lasonolide A has been synthesized efficiently via diastereomeric differentiation, iodocyclization and Julia-Kocieński's sulfone olefination to install its quaternary chiral center, cis-2,6-disubstituted THP and trans-olefin, respectively.     

Solvothermal synthesis and characterisation of new one-dimensional indium and gallium sulphides: [C10N4H26]0.5[InS2] and [C10N4H26]0.5[GaS2]

Two new main group metal sulphides, [C₁₀N₄H₂₆]_0.5[InS₂] (1) and [C₁₀N₄H₂₆]_0.5[GaS₂] (2) have been prepared solvothermally in the presence of 1,4-bis(3-aminopropyl)piperazine and their crystal structures determined by single-crystal X-ray diffraction. Both compounds are isostructural and crystallise in the monoclinic space group P2₁/n (Z=4), with a=6.5628(5), b=11.2008(9), c=12.6611(9) Å and β=94.410(4)° (wR=0.035) for compound (1) and a=6.1094(5), b=11.2469(9), c=12.7064(10) Å and β=94.313(4)° (wR=0.021) for compound (2). The structure of [C₁₀N₄H₂₆]_0.5[MS₂] (M=In,Ga) consists of one-dimensional [MS₂]⁻ chains which run parallel to the crystallographic a axis and are separated by diprotonated amine molecules. These materials represent the first example of solvothermally prepared one-dimensional gallium and indium sulphides.     

三维配位聚合物[C4H12N2]3[PMo12O40]的合成、结构及其电化学性质

The title compound [C4H12N2] 3 [PMo12O40] was synthesized from the hydrothermal reaction and charac-terized by IR, elemental analysis and X-ray signal crystal structural analysis. The crystal of the title complex belongs to trigonal space group R3c with a=1.788 62 nm, c=2.354 3 nm, and V=6.522 62 nm3, Z=6, R1=0.038 4, wR2=0.102 0. The compound consisted of piperazine and PMo12O403-, and the structure is extended to three dimensional framework owing to the hydrogen bond between the O atoms and N atoms. The bulk-modified carbon paste electrode (APM-CPE) using this compound as modifier shows a good electrocatalytic activity toward the oxidation of ascorbic acid(AA). CCDC: 707968.     

[C2B10]---[B12] double cage boron compounds—a new approach to the synthesis of water-soluble boron-rich compounds for BNCT

A new approach in the synthesis of water-soluble boron-rich compounds was proposed. The closo-dodecaborate cage is used as a hydrophilic substitutent providing for the water-solubility of the molecule whereas the carborane cage can be used for attachment to biomolecules using earlier developed methods. The double-cage molecules [o-, m-, and p-CB₁₀H₁₀C(CH₂)₄OB₁₂H₁₁]²⁻ were prepared by the reaction of the tetramethylene oxonium derivative of the closo-dodecaborate anion, [B₁₂H₁₁O(CH₂)₄]⁻, with the corresponding lithiated carboranes. The compounds obtained have doubled the boron contents and could serve for the synthesis of agents for boron neutron capture therapy (BNCT).     

Synthetic studies on bafilomycin A1: stereoselective synthesis of the C12-C17 fragment and its coupling with the C1-C11 subunit

Stereoselective addition of (E)-1-lithio-2-tributylstannylethylene on a chiral cyclic di-t-butylsilyleneketal C₁₄-C₁₇ aldehyde afforded the required Felkin-Anh adduct for the synthesis of the C₁₂-C₁₇ fragment of bafilomycin A₁, the configuration of which was assigned unambiguously. After appropriate coupling with the enantiopure C₁-C₁₁ fragment, the C₁₂-C₁₇ subunit obtained here can be used for the study of the 16-membered macrolide formation either by an acyl activation or an intramolecular Stille reaction. Intermolecular esterification of the 15-OH with an acyl activation of the carboxylic acid of the C₁-C₁₁ fragment, in modified Yamaguchi's conditions, affords here an intermediate for examining an intramolecular Stille coupling.     

Stereoconvergent synthesis of C1-C17 and C18-C25 fragments of bafilomycin A1

The effective syntheses of the enantiomerically pure C1-C17 2 and C18-C25 3 fragments as promising synthetic intermediates of bafilomycin A₁, 1 have been achieved.     

Asymmetric [2,3]Wittig sigmatropic rearrangement involving a chiral azaenolate as the migrating terminus. A simple synthesis of (+)-verrucarinolactone

The diastereo- and/or enantioselection are described in the title rearrangement of the chiral 2-(2-alkenyloxy)methyl 2-oxazolines which eventually provides optically active -hydroxy, γ,δ- unsaturated esters and (+)-verrucarinolactone.     

Synthesis of the C1-C12 fragment of the tedanolides. Selective hydroboration-protonation of allylic alcohol approach

The combination of highly stereoselective vinyllithium addition and hydroboration-protonation of the resulting allylic alcohol permits the preparation of the completely protected C₁-C₁₂ fragment 2 of the novel macrocyclic cytotoxic agent tedanolide 1.     

Formation of metastable crystals of [C4mim][NTf2] and [C6mim][NTf2]

Heat capacities of crystalline 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C₄mim][NTf₂] and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C₆mim][NTf₂] in the range 80 K-T_fus were measured in an adiabatic calorimeter. Anomalies in the heat-capacity curves for the both compounds occurred near 240 K. Positions of the anomalies depended on thermal history of the samples. More stable crystals had higher heat capacities in the range 220-260 K. Below 200 K heat capacities of all the crystals of the same compound were indistinguishable.     

Allylic alcohols formation by oxidation of allylic phenyl tellurides. A possible [2,3] sigmatropic rearrangement of allylic telluroxides

Treatment of cinnamyl, 3-methyl-2-butenyl, and 2-cyclohexenyl phenyl tellurides with an oxidizing agent such as H₂O₂, NaIO₄ or t-BuOOH at room temperature under nitrogen affords 1-phenyl-2-propenol, 2-methyl-3-butene-2-ol, and 2-cyclohexenol as a sole or main product respectively in a high yield. The formation of these allylic alcohols can be best explained by assuming a [2,3]-sigmatropic rearrangement of the intermediate allylic telluroxides. These tellurides also react with oxygen, the formation of α.β-unsaturated carbonyl compounds being much increased in this oxidation.     

Reactions of allylic and propargylic amines and ethers with Zn[Co(CO)4]2

The allylic CN bond of CH₂CHCH₂NEt₂ is cleaved by Zn[Co(CO)₄]₂, producing π-C₃H₅Co (CO)₃. The proparg