1, 3, 4, 4'‐Tetra(triphenylphosphanimin)‐2‐iodo‐2‐butenal‐4‐carboniumiodid, [O=C(NPPh3)C(I)=C(NPPh3)‐C(NPPh3)2]+I‐

Pale yellow single crystals of [O=C(NPPh₃)C(I)=C(NPPh₃)‐C(NPPh₃)₂]⁺I^‐·1.5 thf ( 1 ·1.5 thf) have been obtained by the reaction of INPPh₃ with thallium in thf suspension. They are characterized by IR spectroscopy and by a crystal structure determination. 1 ·1.5 thf crystallizes in the monoclinic space group P2₁/n, Z = 4, lattice dimensions at ‐83?C: a = 1101.7(1), b = 3449.0(2), c = 2000.4(1) pm, β = 104.88(1)?, R₁ = 0.0382. 1 can be understood as a cationic variation of (Z)‐2‐butenale in which all H atoms are substituted by triphenylphosphoraneimine residues and by a iodine atom, respectively.     

New C(2)‐substituted 8‐alkylsulfanyl‐9‐phenylmethyl‐hypoxanthines III

Title compounds were obtained starting from the key imidazole intermediate, 5‐amino‐1‐phenyl‐methyl‐2‐mercapto‐1H‐imidazole‐4‐carboxylic acid amide 5 , readily derived from the base catalyzed rearrangement of a thiazole, 5‐amino‐2‐phenylmethylaminothiazole‐4‐carboxylic acid amide 4 . Alkylation of the thiol function on 5 with phenylmethyl and allylic chlorides gave compounds 6 and 7 respectively. Cyclization of 6 with a variety of esters afforded 8‐phenylmethylthiohypoxanthines, 8–11 . Similarly, 7 was cyclized to 8‐allylthiohypoxanthines, 20–21 . Compound 5 was also cyclized, but formed 8‐mercaptohypox‐anthines, 22–24 . Alkylation of 8‐mercaptohypoxanthines afforded 8‐alkylthiohypoxanthines, 8, 9,25 and 26 (see Scheme 2). Chlorination of 9–11 afforded 16–18 ; adenine 19 was derived from 16 . Oxidation of hypox‐anthines 8–11 with m‐chloroperbenzoic acid gave the corresponding 8‐phenylmethylsulfonyl derivatives 12 ‐ 15 . These derivatives proved resistant to nucleophilic displacement reactions with primary amines.     

(Acetylacetonato‐κ2O,O′)[1‐(4‐bromophenyl‐κC2)‐3‐methylimidazol‐2‐ylidene‐κC2]platinum(II)

The title platinum(II) complex, [Pt(C₁₀H₈BrN₂)(C₅H₇O₂)], has a bidentate cyclometallated phenylimidazolylidene ligand and an acetylacetonate spectator ligand, which form a distorted square‐planar coordination environment around the Pt^II centre. In the solid state, the molecules are oriented in a parallel fashion by intermolecular hydrogen bonding and π–π and C—H...π interactions, while close Pt...Pt contacts are not observed. The structure is only the second example for this new class of compounds.     

Diiodobis(4‐methylpentan‐2‐onato‐C4,O)tin(IV): a comparison with diiodobis(3‐methoxy‐3‐oxopropyl‐C,O)tin(IV)

The title compound, [SnI₂(C₆H₁₁O)₂], contains a six‐coordinate tin centre as a consequence of intramolecular Sn—O interactions. The Sn—O bond lengths range between 2.428 (4) and 2.439 (4) Å.     

Rhodium(I)‐Catalyzed [4 + 2] Cycloaddition Reactions of 2‐Alkylenecyclo‐butanols with Alkynes and (E)‐2‐Nitroethenylbenzene through C(sp2)—C(sp3) Bond Cleavage

An intermolecular [4 + 2] cycloaddition was realized through C—C bond cleavage in the presence of Rh(I) catalyst. The selective ring opening of 2‐alkylenecyclobutanols enables the generation of active alkenylrhodium species, which underwent smooth cross addition over alkynes and (E)‐2‐nitroethenylbenzene, leading to highly substituted all‐carbon six‐membered rings in a single step and in a complete atom economy.     

An Experimental Evidence of a Metal−Metal Bond in μ‐Carbonylhexacarbonyl[μ‐(5‐oxofuran‐2(5H)‐ylidene‐κC,κC)]‐dicobalt(Co−Co)[Co2(CO)6(μ‐CO)(μ‐C4O2H2)]

The orthorhombic crystal structure of [Co₂(CO)₆(μ‐CO)(μ‐C₄O₂H₂)] ( 1 ) was determined at 150 K (Fig. 1). Two C−H⋅⋅⋅O bonds connect the molecules, forming waving ribbons along the b axis. The experimental electron density, determined with the aspherical‐atom formalism, was analyzed with the topological theory of molecular structure. The presence of the Co−Co bond critical point indicates for the first time the existence of a metal−metal bond in a system with bridged ligands. The bond critical properties of the intramolecular bonds and of the intermolecular interactions show features similar to those found in [Mn₂(CO)₁₀], confirming our previously established bonding classification for organometallic and coordination compounds.     

Lipase‐Catalyzed Dynamic Kinetic Resolution of C1‐ and C2‐Symmetric Racemic Axially Chiral 2,2′‐Dihydroxy‐1,1′‐biaryls

We have discovered that the racemization of configurationally stable, axially chiral 2,2′‐dihydroxy‐1,1′‐biaryls proceeds with a catalytic amount of a cyclopentadienylruthenium(II) complex at 35–50 °C. Combining this racemization procedure with lipase‐catalyzed kinetic resolution led to the first lipase/metal‐integrated dynamic kinetic resolution of racemic axially chiral biaryl compounds. The method was applied to the synthesis of various enantio‐enriched C₁‐ and C₂‐symmetric biaryl diols in yields of up to 98 % and enantiomeric excesses of up to 98 %, which paves the way for new developments in the field of asymmetric synthesis.     

Syntheses of β‐C(1→3)‐Glucopyranosides of 2‐ and 4‐Deoxy‐D‐hexoses

The Oshima? Nozaki (Et₂AlI) condensation of isolevoglucosenone ( 4 ) with 2,6‐anhydro‐3,4,5,7‐tetra‐O‐benzyl‐D ‐glycero‐D ‐gulo‐heptose ( 5 ) gave an enone 6 that was converted with high stereoselectivity to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐2,3‐dideoxy‐D ‐arabino‐hexose ( 1 ; 1 : 1 mixture of α‐ and β‐D ‐pyranose), and to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐2,3‐dideoxy‐D ‐lyxo‐hexose ( 2 ; 2.7 : 1.4 : 1.0 : 1.4 mixture of α‐D ‐furanose, β‐D ‐furanose, α‐D ‐pyranose, and β‐D ‐pyranose). The Oshima? Nozaki (Et₂AlI) condensation of levoglucosenone ( 17 ) with aldehyde 5 gave an enone 18 that was converted with high stereoselectivity to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐3,4‐dideoxy‐α‐D ‐arabino‐hexopyranose ( 3 ; single anomer).     

Bipodal 1,1′‐acyl‐3,3,3′,3′‐tetraalkylbis(thiourea) ligands with flexible C3, C4 and C6 spacer groups

In the structures of 3,3,3′,3′‐tetraethyl‐1,1′‐(propane‐1,3‐diyldicarbonyl)bis(thiourea), C₁₅H₂₈N₄O₂S₂, (I), 3,3,3′,3′‐tetraethyl‐1,1′‐(butane‐1,4‐diyldicarbonyl)bis(thiourea), C₁₆H₃₀N₄O₂S₂, (II), and 3,3,3′,3′‐tetrabutyl‐1,1′‐(hexane‐1,6‐diyldicarbonyl)bis(thiourea), C₂₆H₅₀N₄O₂S₂, (III), compound (I) displays resonance‐assisted hydrogen bonding, (II) exhibits an inversion centre, and both (II) and (III) are characterized by intermolecular hydrogen bonds between the carbonyl O atoms and thioamide H atoms, leading to chains of hydrogen‐bonded molecules throughout the structures. The accurate structural data for these molecules is expected to assist in molecular modelling and other studies currently in progress.