Total syntheses of zaragozic acids A and C by a carbonyl ylide cycloaddition strategy

A carbonyl ylide cycloaddition approach to the squalene synthase inhibitors zaragozic acids A and C is described. The carbonyl ylide precursor 8 was synthesized starting from di-tert-butyl D-tartrate (47) via an eleven-step sequence involving the regioselective reduction of the mono-MPM (MPM=4-methoxybenzyl) ether 48 with LiBH4 and the diastereoselective addition of sodium tert-butyl diazoacetate to alpha-keto ester 10. The reaction of alpha-diazo ester 8 with 3-butyn-2-one (40) in the presence of a catalytic amount of [Rh2(OAc)4] gave the desired cycloadduct 59 as a single diastereomer. The dihydroxylation of enone 59 followed by sequential transformations permitted the construction of the fully functionalized 2,8-dioxabicyclo[3.2.1]octane core 5. Alkene 79 derived from 5 serves as a common precursor to zaragozic acids A (1) and C (2), since the elongation of the C1 alkyl side chain can be attained by olefin cross-metathesis, especially under the influence of Blechert's catalyst (85).     

Regioselective synthesis of linalyl compounds via addition reaction of geranyl bromide and tin with carbonyl compounds

Linalyl alkyl or aryl carbinols were regioselectively synthesized by the reaction ofgeranyl bromide and powdered tin with aldehydes and ketones.     

Synthesis of vinylogous carbamates by rhodium(II)-catalyzed olefination of tertiary formamides with a silylated diazoester

Treatment of tertiary formamides with a silylated diazoester in the presence of a rhodium(II) catalyst leads to the formation of 3-amino-2-silyloxyacrylates in good yield. No olefination is observed if a nonsilylated diazo compound is employed. [reaction: see text]     

Synthesis of unsaturated carbonyl compounds via a chromium-mediated allylic oxidation by 70% tert.butylhydroperoxide

Alkenes were converted into α,β-unsaturated carbonyl compounds using excess of tert.butylhydroperoxide and catalytic amounts of chromium^VI oxide at room temperature. Fair yields and conversions were obtained from Δ⁵-steroids while allylic oxidation of acyclic alkenes was less efficient. Epoxidation of the double bond, sometimes observed, remained a minor reaction pathway.     

Conformational studies by nuclear magnetic resonance—V: 13C spectra and structural problems of enamino carbonyl compounds

A ¹³C magnetic resonance investigation of 22 compounds of the general formula O?C¹(R¹)C²(R²)?C³(R³) NR⁴R^4′ has been carried out in order to confirm the conformational assignments estimated previously by PMR and IR spectroscopy. The effects of nonplanarity and hindered rotation have been discussed based on chemical shifts and shapes of the C¹, C² and C³ signals.     

A new pathway in the reaction of disilene with carbonyl compounds: an 'ene' reaction instead of cycloaddition

The 3H-disilagermirene, (tBu2MeSi)4GeSi2, reacts with alpha-hydrogen containing carbonyl compounds (acetophenone, butane-2,3-dione) by an 'ene'-reaction pathway followed by isomerization or insertion reactions, representing a new mode in the reaction of disilenes with carbonyl compounds.     

Synthesis and characterization of the new thermosetting monomers and phthalocyanine polymers with ester—imide linkages

The study described here deals with the methods of synthesis of two new bisphthalonitrile derivatives with ester—imide linkages and their polymerization. Optimum conditions for the synthesis and characterization of the bisphthalic anhydrides, bisphthalonitriles, and polymers are developed using IR spectral, differential scanning calorimetric, dynamic thermogravimetric analytical, and mass spectral studies. These new polymers showed good thermal stability and chemical inertness. The polymers showed char yield of 50% at 800°C in nitrogen atmosphere. These thermosetting phthalocyanine polymers are expected to be useful in various applications such as the production of moulded articles and laminates.     

Photochemical Reactions. 129th Communication. Photochemistry of a conjugated diepoxydiene: Product formation via carbonyl ylide and carbene intermediates with participation of neighbouring epoxy functions

On singlet excitation (λ=254 nm, acetonitrile) the diepoxydiene (E)- 7 undergoes photocleavage to the carbonyl ylide VII and the carbenes X and XI . The carbonyl ylide VII rearranges to the thermally labile dioxabicyclo [3.2.1]octene 20 or fragments via VIII to the aldehyde 9 and propyne. The carbene X , showing behaviour typical of vinyl carbenes, undergoes addition to the adjacent double bond furnishing the cyclopropene 11 . The carbene XI , however, undergoes an insertion reaction into the neighbouring oxirane C,C-bond leading to the oxetene (E)- 21 which can be isolated at ?78°, but at room temperature is rapidly transformed to the aldehyde 10 . On triplet excitation (acetone, λ>280 nm), however, (E)- 7 shows the typical behaviour of epoxydienes, undergoing C, O-cleavage of the oxirane and isomerization to 22, 23 and (E/Z)- 24 .     

A highly regio- and stereo-selective [3+2] annulation of allylic compounds and 2-substituted 1,1-dicyanoalkenes through a catalytic carbon-phosphorus ylide reaction

A highly regio- and stereo-selective phosphine-catalyzed [3+2] annulation reaction between allylic compounds and 2-substituted 1,1-dicyanoalkenes through a catalytic phosphorus ylide reaction was developed. This reaction has the total reversed regioselectivity compared to that of the reactions of activated alkenes without the 2-substituents or reactions using the allenoates as the C3 component.     

Reactions of trialkylsilanes with alcohols and carbonyl compounds,catalyzed by fluoride anion

Conclusions In anhydrous acetonitrile the ionic potassium, cesium and tetraethylammonium fluorides catalyze the reactions of trialkylsilanes with alcohols and carbonyl compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 932–934, April, 1973.     

Synthesis of resveratrol, DMU-212 and analogues through a novel Wittig-type olefination promoted by nickel nanoparticles

A novel synthesis of resveratrol, DMU-212 and analogues is presented using benzyl alcohols as phosphorus ylide partners in a one-pot Wittig-type olefination reaction promoted by nickel nanoparticles.     

Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species

Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 degrees C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.     

Generation of allylic indium by hydroindation of 1,3-dienes and one-pot reaction with carbonyl compounds

A hydroindation of 1,3-dienes by dichloroindium hydride (HInCl2) generates allylic indiums that react with carbonyl or imine moieties in a one-pot treatment. The former reaction proceeds in a radical manner, and the latter is ionic allylation. Moreover, both reactions require no additives such as radical initiators, Lewis acids, or transition metal catalysts.     

2-Phenoxyethanol derived diselenide and related compounds; synthesis of a seven-membered seleninate ester

Syntheses of several diorganodiselenides and, in particular, a seven-membered cyclic seleninate ester derived from 2-phenoxyethanol are described. The seleninate ester was obtained from allyl (2-(2-hydroxyethoxy)phenyl) selenide through a series of oxidation and [2,3] sigmatropic rearrangement steps. The ester exhibits good GPx-like activity in the coupled reductase assay.     

A two-step synthesis of allylic syn 1,3-diols via an intramolecular oxa-Michael reaction followed by a modified Julia olefination

A two-step process for the synthesis of allylic syn 1,3-diols is developed. An intramolecular oxa-Michael reaction onto vinyl heteroaromatic sulfones allows the diastereoselective formation of 1-sulfonyl 2,4-diols protected as benzylidene acetals. These sulfones are then engaged in a modified Julia olefination to furnish the olefins contiguous to the benzylidene acetal ring with good E/Z selectivity.     

Synthesis of cationic ethylenic and dienic complexes of metal carbonyl compounds with a metal-metal bond

Conclusions A method was developed for the synthesis of cationic olefinic and dienic complexes of transition metals entailing the simultaneous reaction of an acid and unsaturated organic substrate with a metal carbonyl compound containing a metal-metal bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1440–1443, June, 1986.     

A novel synthesis of alkyl vinyl ketones and divinyl ketones from carbonyl compounds by three-carbon homologation

Alkyl vinyl ketones and divinyl ketones are synthesized from carbonyl compounds and 1-chloro-3-phenylthiopropyl phenyl sulfoxide as a three-carbon homologating agent in good overall yields.     

Reaction of N,N′-carbonyldiimidazole and N,N′-thionyldiimidazole with carbonyl compounds: a new imidazole transfer reaction

Ketones and aldehydes undergo facile addition reaction with N,N′-thionyldiimidazole to give the monoimidazole and the diimidazole.