Novel Reactions of Organomolybdenum and Organotungsten Compounds: Additive–Reductive Carbonyl Dimerization,Spontaneous Transformation of Methyl Ligands into μ-Methylene Ligands,and Selective Carbonylmethylenation

Hitherto there was no reaction known that permits transformations of R¹R²-CO → 0.5 R¹R²R³C–CR¹R²R³ in one step. This type of additive–reductive carbonyl dimerization is now possible using alkoxy(alkyl)tungsten(v) complexes with aromatic, heteroaromatic or α,β-unsaturated aldehydes and ketones. When a corresponding phenyl complex was employed in a test experiment, it was revealed that an aliphatic ketone could be used as the substrate in this reaction. A second interesting type of reaction is the transformation of CH₃ ligands into μ-CH₂ ligands, which occurs during the treatment of MeLi or Me₃Al with molybdenum or tungsten chlorides (oxidation states VI and V, for Mo additionally IV) at low temperatures with liberation of CH₄. Here, the question arises as to whether the intermediate involved has a terminal CH₂ ligand (Schrock carbene complex) or a μ-CH₃ ligand (CH₃ bound by a two-electron three-center bond to two metal atoms). Of all the μ-CH₂ complexes obtained, those which were synthesized by the action of MeLi on molybdenum chlorides can be recommended as reagents for carbonylmethylenation of aldehydes and ketones. They display high selectivity, very low basicity, a surprising resistance to protons, they are readily available, can be easily modified and, as regards their selective behavior, they have been investigated more thoroughly than other readily accessible carbonylmethylenation reagents of comparable selectivity. The results of NMR spectroscopic investigations on the structure of the μ-CH₂ complexes, and associated reaction mechanisms are discussed. A survey of carbonylmethylenation reagents, which have been reported in the literature, permits comparisons to be made with carbonylmethylenating molybdenum and tungsten complexes.     

双环烯醚的合成及其性质的研究

由内酯2和Tebbe试剂反应合成了双环烯醚化合物5-苄氧基-2,8-二亚甲基-3,4,9,10-四氢-2H,8H-苯并[1,2-b; 3,4-b']二吡喃(3), 环烯醚在酸性条件下很容易水解和异构化, 在酸存在下外环烯醚3于10 min内转化为内环烯醚4, 较长的反应时间只能得到水解物或其它分解产物.     

Ring-closing metathesis as a new methodology for the synthesis of monomeric flavonoids and neoflavonoids

Basic flavonoid (flavene) and neoflavonoid (neoflavene) skeletons were successfully synthesized using ring-closing metathesis, showing that this methodology can be used as a central synthetic tool for the synthesis of at least two of the three basic flavonoid classes.     

双冠醚的研究——Ⅳ.N,N-氨二乙酸类化合物与苯并-15-冠-5在多聚磷酸中生成亚甲基双(4'-苯并-15-冠-5)的反应

在多聚磷酸中,苯并冠醚与一元酸或二元酸反应,缩合而生成相应的酰基衍生物。本文用氨或胺衍生的N,N-胺二乙酸类化合物与苯并-15-冠-5和多聚磷酸相反应,探讨了这种体系的反应特点。所用的N,N-胺二乙酸为分析化学上几种常用的氨羧络合剂     

New chiral spiro[2.5]octanones as products of methylenation of (3<Emphasis Type="Italic">R</Emphasis>, 6<Emphasis Type="Italic">R</Emphasis>)-2-arylidene-6-isopropyl-3-methylcyclohexanones with dimethylsulfoxonium methylide. Synthesis,stereochemistry, and behavior in liquid-crystalline systems

Methylenation of (3R,6R)-2-(4-X-benzylidene)-6-isopropyl-3-methylcyclohexanones (X = F, Cl, Ph) with dimethylsulfoxonium methylide occurs stereoselectively to give 1(S)-(4-X-phenyl)-5(R)-isopropyl-8(R)-methyl-3(R)-spiro[2.5]octanones, whose stereochemistry was established by ¹H NMR spectroscopy. The configuration of the chiral centers in the cyclohexanone fragment and its preferred conformation (methyl is axial and isopropyl is equatorial) in the products do not change with respect to the starting enones. The mutual trans-arrangement of the carbonyl and aryl groups at the newly formed three-membered ring was established; the aryl group also occupies the trans-position with respect to the axial methyl group of the cyclohexanone fragment. Using methylenation of the compound with X = Ph as an example, a mixture of by-products resulting from oxidative hydroxylation at the α-position relative to the carbonyl group was isolated. The resulting chiral spiro[2.5]octanones induce a helical supramolecular ordering in the nematic mesophase of 4-pentyl-4′-cyanobiphenyl and exhibit a twisting power only somewhat (by 20–30%) lower than the starting enones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2331–2341, October, 2005.     

The reaction of salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides with dihalomethanes

Methylene-bis[N′-oxydiazene-N-(β-hydroxyalkyl)N-oxides] were synthesized by the reaction of salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides with diahalomethanes. The effect of the nature of the starting reagents and the reaction condtions on the yields of the target compounds was studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2266–2269, November, 1998.     

Reaction ofN,N-bis(chloromethyl)amides withN,N′-diacylated alkene(arylene)diamines

Reactions ofN,N-bis(chloromethyl)amides withN,N′-diacyl derivatives of ethylenediamine (oro-phenylenediamine) result in formation of the corresponding 1,3,5-triacylated perhydro-1,3,5-triazepines (or their benzoanalogs) or 1,3-diacylated imidazolidines (or their benzoanalogs). Reactions ofN,N-bis(chloromethyl)amides withN,N′-ditosylated trimethylenediamine occur in a similar way. The direction of the reactions depends on the type of the acyl substituents and the strength of the bases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2270–2273, November, 1998.     

Tris(trimethylsilylmethyl)alane: an aldehyde selective peterson methylenation reagent

Tris(trimethylsilylmethyl)alane (TTMA) is a rapid, efficient, and highly aldehyde-selective trimethylsilylmethylating reagent. A solid lithium halide complex of the reagent, TTMA · 3LiBr (TTMAs), is particularly effective in this transformation to the Peterson alcohol intermediate.