Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.     

Chemical control of the photochromic reactivity of diarylethene derivatives

Photochemically inactive diarylethene derivatives having a N-(O-hydroxyphenyl) group underwent photochromic reaction when they were esterified by the addition of acetic anhydride.     

Photoreactions of β-aziridinylacrylonitriles and acrylates with alkenes: formation of head-to-head adducts and application to the preparation of pyrrolizidine alkaloid

The photochemical C,C-bond cleavage of N-benzyl β-aziridinylacrylonitrile 1 and acrylate 2 and the subsequent [3+2] cycloaddition with electron-deficient alkenes afforded head-to-head adducts selectively and efficiently. Irradiation of N-phenyl aziridine 3 with acrylonitrile gave adducts, but photoreaction of N-benzoyl aziridine 4 and thermal reactions of 3 and 4 with alkenes yielded C(γ),N-cleaved products instead of cycloadducts. N-trityl aziridine 5 also reacted with electron-deficient alkenes, affording 2,3-cis-pyrrolidine derivatives exclusively. A formal synthesis of a pyrrolizidine alkaloid, isoretronecanol (27), starting from 5 was achieved in a convenient manner.     

Iridium-catalyzed reaction of aroyl chlorides with internal alkynes to produce substituted naphthalenes and anthracenes

Benzoyl chlorides efficiently react with 2 equiv of dialkylacetylenes as well as diphenylacetylene in the presence of an iridium catalyst accompanied by decarbonylation to produce 1,2,3,4-tetrasubstituted naphthalenes in good yields. Use of 2-naphthoyl chlorides selectively affords the corresponding anthracene derivatives.     

New types of Br?nsted acid-base ionic liquids-based membranes for applications in PEMFCs.

A series of ionic liquids (ILs) are prepared by neutralizing tertiary amines with N,N-bis(trifluoromethanesulfonyl)imide (HTFSI). As demonstrated by thermal and electrochemical characterizations, these ILs have very good temperature stability and a high ionic conductivity, that is, of the order of 10(-2) S cm-1. By incorporating these ILs into a poly(vinylidenfluoride-co-hexafluoropropylene) polymer matrix, membranes with a high melting temperature, high decomposition point and with an ionic conductivity of about 10(-2) S cm-1 at 140 degrees C, are obtained. These IL-based, proton-conducting membranes are proposed as new polymer electrolytes for high-temperature polymer electrolyte membrane fuel cells (PEMFCs).     

Practical synthesis of Dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate

An efficient and reliable procedure for the preparation of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh2(S-PTTL)(4), a universally effective catalyst for a range of enantioselective carbene transformations, is described. The N-phthaloylation of (S)-tert-leucine by the method of Bose with essentially no racemization is a key to this process.     

2'-O-[2-[N,N-(dialkyl)aminooxy]ethyl]-modified antisense oligonucleotides

[structure] Oligonucleotides with two novel modifications, 2'-O-?2-[N, N-(dimethyl)aminooxy]ethyl? (2'-O-DMAOE) and 2'-O-?2-[N, N-(diethyl)aminooxy]ethyl? (2'-O-DEAOE), have been synthesized. These modifications exhibit high binding affinity to target RNA (and not to DNA) and enhance the nuclease stability of oligonucleotides considerably with t(1/2) > 24 h as a phosphodiester.     

Catalyzed intramolecular olefin insertion into a carbon-carbon single bond

Intramolecular insertion of a C-C double bond into a C-C single bond was achieved by treatment of cyclobutanone bearing an o-styryl group at the 3-position with a catalytic amount of a cationic rhodium(I)-dppp complex. Initially, rhodium is inserted between the carbonyl carbon and the alpha-carbon of the cyclobutanone. Intramolecular coordination of the vinyl group results in its migratory insertion into the C-Rh linkage. Reductive elimination affords benzobicyclo[3.2.1]octan-3-one. Notably, a ring-opened alpha,beta-unsaturated ketone was obtained when dppe was used instead of dppp. In this reaction, rhodium cleaved the bond between the alpha sp3 carbon and the beta sp3 carbon of the cyclobutanone. The coordinating vinyl group directs this new regioselectivity of cleavage observed with the dppe ligand.     

Novel use of organotin halide-base complex in organic synthesis. Cycloaddition reaction of oxetane with isocyanates.

Cycloadditions of oxetanes with isocyanates were markedly accelerated by the complex of Bu₂SnI2 and Ph₃P=O which could be readily handled and hardly caused a trimerization of isocyanates, yielding oxazin-2-ones under neutral and mild reaction conditions.     

Ladderlike ferromagnetic spin coupling network on a pi-conjugated pendant polyradical

A poly(9,10-anthryleneethynylene)-based polyradical with two pendant stable phenoxyls in one anthracene skeleton was newly synthesized via polymerization of the corresponding bromoethynylanthracene monomer using a Pd(0) catalyst. The average molecular weight of the polymer reached M(n) = 5 x 10(3) and was soluble in common organic solvents. The polyradical was prepared from the corresponding hydroxyl precursor polymer and was appropriately stable at room temperature. The ESR spectrum of the corresponding monomeric radical suggested an effectively delocalized spin density distribution on the backbone anthracene. The magnetization and the static magnetic susceptibility of the polyradical were measured using a SQUID magnetometer. The large average spin quantum number (S = (5)/(2)) of the polyradical indicated that the ferromagnetic spin coupling network of the polyradical had spread throughout the pi-conjugated chain and that it was considerably insensitive to spin defects.