A novel synthesis of allyl and propargyl selenides in aqueous media promoted by indium

Allylic and propargyl bromides react smoothly with diorganyl diselenides in aqueous media to give allylic and propargyl selenides in moderate to good yields. The reaction need not be carried out in inert atmosphere. The speed is quicker than the same reactions in organic media.     

Generation of allyl Grignard reagents via titanocene-catalyzed activation of allyl halides

A protocol for the generation of allyl Grignard reagents via the catalytic activation of allyl halides is described herein. Subsequent nucleophilic addition to carbonyl derivatives provided the desired homo allylic alcohols in excellent yields (84-99%). Evidence suggests that titanocene dichloride catalyzes the formation of an allyl Grignard species which reacts solely with the carbonyl electrophile as evidenced by the complete absence of Würtz coupling. This methodology will have wide-ranging applicability in the generation of highly reactive organometallic reagents.     

Reactions of tertiary propargyl alcohols with sodium halides under oxidative conditions

The study of the reactions of tertiary propargyl alcohols with sodium halides under oxidative conditions is presented. With sodium iodide, α-iodoenones were formed, however, with sodium bromide or chloride the α-haloenones were only formed in low yields under anhydrous conditions. Conversely, upon addition of water to the reaction mixtures, α,α-dibromoketones and α,α-dichloroketones were formed in good yields, but α,α-diiodoketones were not observed.     

A facile synthesis of N-sulfonyl and N-sulfinyl aldimines under Barbier-type conditions

A convenient synthesis of N-sulfonyl- and N-sulfinylimines by the condensation of aldehydes with sulfonyl or sulfinyl amides in the presence of benzyl bromide and zinc dust at room temperature under the Barbier-type conditions is reported. The procedure is lauded by its simplicity and adaptability to aromatic, alpha,beta-unsaturated, and aliphatic aldehydes.     

One-pot amide synthesis from allyl or benzyl halides and amines by Pd-catalysed carbonylation

Amides can be prepared from allyl or benzyl halides and primary or secondary amines, using Pd(0) catalyst under CO pressure, in a one-pot synthesis. The reaction proceeds through the acyl palladium halide formation which undergoes an acylic nucleophilic substitution from the amine.     

A mild synthesis of vinyl halides and gem-dihalides using triphenyl phosphite-halogen-based reagents

A new application of (PhO)3P-halogen-based reagents to the synthesis of vinyl halides and gem-dihalides is described. Vinyl halides were prepared in good to excellent yields from enolizable ketones, whereas aldehydes afforded the corresponding gem-dihalides. The halogenation proceeded smoothly under mild conditions.     

钐试剂在合成中的应用I. 金属钐作用下烯丙基和苄基卤代物与羰基化合物的反应

本文研究了金属钐作用下的Barbier型反应。结果表明, 经氯化汞活化的金属钐对酮类化合物与烯丙基或苄基卤代物的反应很有效, 可高产率地生成叔醇。此反应有很好的区位选择性和化学选择性, 与α, β-不饱和酮的反应未发现1, 4-加成产物生成, 与环上有卤素(Br, Cl)取代的芳香酮反应, 取代基不受影响。产物的形成可能通过了有机钐中间体。     

Palladium-catalyzed oxidative carbonylation of alkyl and aryl indium reagents with CO under mild conditions

CO now can react with organoindium reagents. A novel palladium-catalyzed oxidative carbonylation reaction of organoindium reagents by CO gas with desyl chloride as oxidant was developed in supplementation with the classical methods for preparation of carboxylic acid derivatives. Primary, secondary alkyl indium reagents with beta-hydrogens and aryl indium reagents were suitable substrates, and the reaction could be carried out at 60 degrees C under 50 psi CO. Carbonylation of alkyl indium reagents can occur smoothly without additional base. Although the indium reagents were prepared from corresponding Grignard reagents (at low temperature), they displayed full compatibility with various functional groups under the protic reaction conditions. Preliminary mechanistic studies including stoichiometric and catalytic reaction examination provided evidence to support the operation of the mechanism consisted of oxidative addition of deslyl chloride to Pd(0) and quick tautomerization to give a palladium enolate species II (ROPdCl), displacement of the enolate group in II by R(2)OH, followed by CO insertion to give alkoxycarbonyl palladium complex V, which undergoes transmetalation with R(1)(3)In and reductive elimination to afford the product and a Pd(0) species. In this mechanism, the alkoxycarbonyl group was transferred to the palladium center prior to the alkyl group, different from traditional ways initiated from oxidative addition of alkyl halides to a Pd(0) species.     

Silver-catalyzed [2,3]-rearrangement of halonium ylides derived from allyl and propargyl halides and alkyl diazoacetates

A silver(I) complex derived from a polyfluorinated tris(pyrazolyl)borate effectively catalyzes carbene transfer to allylic and propargylic halides, leading to the formation of alpha-haloacetate derivatives.     

Allylation of aldiminomercaptotriazinones using allyl halides and allylmetal compounds

Allylation of 4‐amino‐3‐mercapto‐6‐methyl‐4H‐1,2,4‐triazin‐5‐one ( 1 ) and its arylideneamino derivatives 5 was performed through two different methods. Reaction of 1 and 5 with allylic bromides 2 in the presence of sodium ethoxide afforded a mixture of S‐ and N‐allylated products. Treatment of arylimines 5 with allylic zinc bromides 9 and triallylborane reagents 12 did not affect the hetero‐ring opening but the CN bond of the lateral chain underwent the addition reaction yielding the C‐allylated products 10 . © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:280–287, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10144     

Kinetics and mechanisms of the allyl + allyl and allyl + propargyl recombination reactions

The kinetics and mechanisms of the self-reaction of allyl radicals and the cross-reaction between allyl and propargyl radicals were studied both experimentally and theoretically. The experiments were carried out over the temperature range 295-800 K and the pressure range 20-200 Torr (maintained by He or N(2)). The allyl and propargyl radicals were generated by the pulsed laser photolysis of respective precursors, 1,5-hexadiene and propargyl chloride, and were probed by using a cavity ring-down spectroscopy technique. The temperature-dependent absorption cross sections of the radicals were measured relative to that of the HCO radical. The rate constants have been determined to be k(C(3)H(5) + C(3)H(5)) = 1.40 × 10(-8)T(-0.933) exp(-225/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.088) and k(C(3)H(5) + C(3)H(3)) = 1.71 × 10(-7)T(-1.182) exp(-255/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.069) with 2σ uncertainty limits. The potential energy surfaces for both reactions were calculated with the CBS-QB3 and CASPT2 quantum chemical methods, and the product channels have been investigated by the steady-state master equation analyses based on the Rice-Ramsperger-Kassel-Marcus theory. The results indicated that the reaction between allyl and propargyl radicals produces five-membered ring compounds in combustion conditions, while the formations of the cyclic species are unlikely in the self-reaction of allyl radicals. The temperature- and pressure-dependent rate constant expressions for the important reaction pathways are presented for kinetic modeling.     

Organozinc reagents from polyfluoroarenes: Preparation and reactions with allyl halides. Synthesis of allylpolyfluoroarenes

Organozinc compounds of the general formula Ar_FZnX (X = Cl, Ar_F) were synthesized by reactions of Zn with chloropolyfluoroarenes and of Zn/SnCl₂ with polyfluoroarenes. Polyflorinated organozinc compounds reacted with allyl chloride and allyl bromide to give the corresponding allyl-substituted polyfluoroarenes. The reactions with allyl chloride were carried out in the presence of copper(I) salts (CuCl or CuI).     

Liquid-phase synthesis of cyclic diene diepoxides using metal halides and hydrogen peroxide

Optimal conditions were found for induced hydroxyhalogenation of cyclic dienes (tetrahydroindene, 4-vinylcyclohexene and 5-vinyl- and 5-cyclohexenylbicyclo[2.2.1]hept-2-enes) in the system [MHlg-HA or HHlg]-H₂O₂ (or NaClO). Dehydrohalogenation of the chloro- and bromohydrins thus obtained with powdered potassium carbonate gave the corresponding diepoxy derivatives, and their hydrolysis led to mixtures of stereoisomeric tetrahydric alcohols.     

Different C-glycosidation products of glucal with alkynyl or propargyl silanes under acidic conditions

Propargylic and acetylenic silyl groups on propyne control the C-glycosidation products depending on the trimethylsilyl and triisopropylsilyl groups used. Some mechanistic discussions are included. [reaction: see text]     

Tris(allyl) indium compounds: synthesis and structural characterization

Allyl and 2-methylallyl indium compounds were prepared by salt metathesis starting from indium trichloride and a Grignard reagent. They are highly fluxional in solution and reveal coordination numbers of the indium atoms of four and five in the solid state.     

Rhenium-catalyzed coupling of propargyl alcohols and allyl silanes

A mild method for the regioselective coupling of propargyl alcohols and allylsilanes is described. The method employs an air- and moisture-tolerant rhenium-oxo complex ((dppm)ReOCl3) as a catalyst for the formation of sp3-carbon-sp3-carbon bonds without the need for prior activation of the propargyl alcohol as a halide or pseudohalide. The stability of the high oxidation state rhenium complex allows for simple reisolation and reuse of the catalyst. A broad range of functional groups is tolerated including aryl halides, olefins, esters, and acid-labile functional groups such as acetals. Furthermore, displacement of the alcohol occurs preferentially even in the presence of other electrophiles such as primary alkyl halides and conjugated esters. The use of enantiopure crotylsilanes as coupling partners allows for the asymmetric construction of two adjacent stereocenters. The potential of this reaction is demonstrated in an asymmetric synthesis of delta-lactone, di-O-methylcalopin.     

Heteropolyacid-catalyzed direct deoxygenation of propargyl and allyl alcohols

The combination of H(3)[PW(12)O(40)]·nH(2)O (1 mol %) and Et(3)SiH led to the direct catalytic deoxygenation of propargyl alcohols, in which proper solvent selection Cl(CH(2))(2)Cl vs CF(3)CH(2)OH was the key to obtaining better product yields. Under similar conditions, the deoxygenation of allyl alcohols proceeded to give thermodynamically stable alkenes with migration of the double bonds in good yields.