Practical Stannylation of Allyl Acetates Catalyzed by Nickel with Bu3SnOMe

A practical and scalable nickel‐catalyzed allylic stannylation of allyl acetates with Bu₃SnOMe is described. A variety of acyclic and cyclic allyl acetates, even with base‐sensitive moieties, undergoes the stannylation by using NiBr₂/4,4′‐di‐tert‐butylbipyridine (dtbpy)/Mn catalyst system to afford highly functionalized allyl stannanes with excellent regioselectivity and yields. Furthermore, the scope of protocol is also extended by the reaction of propargyl acetates, giving rise to propargyl or allenyl stannanes. Additionally, a unique diastereoselectivity using the nickel catalyst different from the palladium was demonstrated for the stannylation of cyclic allyl acetates. In the reaction, inexpensive and stable nickel complexes, abundant reductant (Mn), and atom‐economical stannyl source were used.     

Alkylation of 4-picolinium salts under phase transfer conditions

Alkylation of 1-ethyl-4-methylpyridinium bromide by allyl, benzyl and propargyl chlorides has been effected under conditions of phase transfer catalysis in a solid phase-liquid system (K₂CO₃-CHCl₃). Using the example of alkylation by allyl chloride, the effect of the concentration and the nature of the catalyst, the concentration of the base, and the temperature on the yield of mono-, di-, and trisubstituted products has been studied. The reactivity of the alkyl chlorides increases in the order allyl < benzyl < propargyl. When the reaction is carried out in a liquid—liquid system (25% aqueous NaOH-CHCl₃) the Br- anion of the starting material is replaced by Cl^–, in contrast to the K₂CO₃-CHCl₃ system.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 520–524, April, 1989.     

Novel gallium-mediated C3-allylation of indoles and pyrroles in aqueous media promoted by Bu4NBr

A mild and efficient protocol for the coupling of indoles and pyrroles with allyl halides such as allyl bromide, crotyl bromide and propargyl bromide in the presence of gallium metal in a Bu₄NBr-DMF-H₂O system has been developed. The reaction is equally effective when cadmium is used in lieu of gallium and the corresponding 3-allyl indoles and 3-allyl pyrroles were obtained in almost comparable yields.     

Indium-mediated vic-diallylation/propargylation of phenacyl bromides: a facile synthesis of 4-arylocta-1,7-dien-4-ol derivatives

Phenacyl bromides undergo smooth vic-diallylation and dipropargylation with allyl and propargyl indium reagents generated in situ from metallic indium and allyl or propargyl bromide to produce 4-arylocta-1,7-dien-4-ol derivatives in good yields. Phenacyl chloride and azide also participated effectively in bis-allylation. Similar results are also obtained from in situ generated allyl or propargyl zinc bromide.     

Stereospecific synthesis of a family of novel (E)‐2‐aryl‐1‐silylalka‐1,4‐dienes or (E)‐4‐aryl‐5‐silylpenta‐1,2,4‐trienes via a cross‐coupling of (Z)‐silyl(stannyl)ethenes with allyl halides or propargyl bromide

Stereospecific synthesis of a family of novel (E)‐2‐aryl‐1‐silylalka‐1,4‐dienes or (E)‐4‐aryl‐5‐silylpenta‐1,2,4‐trienes via a cross‐coupling of (Z)‐silyl(stannyl)ethenes with allyl halides or propargyl bromide is described. In the reaction with allyl bromide, either a Pd(dba)₂? CuI combination (dba, dibenzylideneacetone) in DMF or copper(I) iodide in DMSO–THF readily catalyzes or mediates the coupling reaction of (Z)‐silyl(stannyl)ethenes at room temperature, producing novel vinylsilanes bearing an allyl group β to silicon with cis ‐disposition in good yields. Allyl chlorides as halides can be used in the CuI‐mediated reaction. CuI alone much more effectively mediates the cross‐coupling reaction with propargyl bromide in DMSO–THF at room temperature compared with a Pd(dba)₂? CuI combination catalysis in DMF, providing novel stereodefined vinylsilanes bearing an allenyl group β to silicon with cis ‐disposition in good yields. Copyright © 2008 John Wiley & Sons, Ltd.     

A simple organocobalt mediated synthesis of substituted 3-oxabicyclo[3.3.0]oct-6-en-7-ones

A range of substituted propargyl alcohols form ethers with allyl bromide in good yields; conversion of these ethers to the alkyne hexacarbonyl dicobalt complexes using Co₂(CO)₈, followed by intramolecular cyclisation gives substituted 3-oxabicyclo[3.3.0]oct-6-en-7-ones (4a–4e) in fair to moderate yields.     

Synthesis and Structural Studies of Cyclotriveratrylene Derivatives

Cyclotriveratrylene (CTV) derived host molecules with ethyl, propyl, allyl or propargyl functional groups have been synthesised using standard or solventless reaction methodologies. The known structural and clathrate chemistry of cyclotriveratrylene (CTV) and these analogues has been extended. Crystal structures of the hexa(ethyl), tri(ethyl), tri(propargyl) analogues have been determined, and show either intra-cavity host-guest binding or self-stacking motifs. Two new clathrates of CTV have also been structurally characterised, namely CTV.(DMSO)₂.(H₂O)₂ with intra-cavity complexation of DMSO, and CTV.(EtOH)_0.25 which has a γ-phase CTV structure.     

α-(Benzotriazol-1-YL)Propargyl Ethyl Ethers: Novel Precursors to Enediynes,Enynes and Dienynes

Deprotonated 1-(benzotriazol-1-yl)propargyl ethyl ethers react with propargyl, allyl and alkyl bromides to give the expected substituted derivatives 2, 4 and 9, respectively. Subsequent eliminations of the benzotriazolyl group upon treatment with NaH or ZnBr₂, and elaboration of the acetylene group, generate ethoxy substituted enediynes 3, 6, 8, dienynes 7 and enynes 12. Grignard reagents or LiAlH₄ convert 9 into α-ethoxy substituted alkynes 10 and 11.     

NbCl5 mediated deprotection of methoxy methyl ether

An efficient cleavage of methoxy methyl ether using NbCl₅ is described. This protocol works efficiently with MOM ethers of alkyl, allyl, propargyl, benzyl alcohol and phenol derivatives. MOM esters are also found to be effectively cleaved under the present conditions.     

Elaboration of the ether cleaving ability and selectivity of the classical Pearlman's catalyst [Pd(OH)2/C]: concise synthesis of a precursor for a myo-inositol pyrophosphate

The cleavage of propargyl, allyl, benzyl, and PMB ethers by Pd(OH)₂/C can be tuned in that order, by varying the reaction conditions. Other moieties such as C-C double bonds, esters, trityl ether, p-bromo and p-nitrobenzyl ethers are stable to these reaction conditions. Cleavage of allyl ethers can be made catalytic by using 1:1 mixture of Pd(OH)₂/C and Pd/C. The synthetic potential of the selective ether cleaving ability of Pd(OH)₂/C, essentially under neutral conditions, has been demonstrated by an efficient synthesis of a precursor for the preparation of an inositol pyrophosphate derivative.     

STEREOSELECTIVE SYNTHESIS OF PSEUDOGLYCAL C-GLYCOSIDES VIA TRICHLOROACETIMIDATE ACTIVATION OF GLYCALSa

A variety of functionalized pseudoglycal C-glycosides (C-pseudoglycals or C-hex-2-enopyranosides) have been obtained in excellent yield and stereoselectivity from the trimethylsilyl triflate (Me ₃SiOTf) catalyzed reaction of trichloroacetimidate derivative 2 with silylated nucleophiles such as allyl and propargyl silanes and silyl enol ethers.

     

Selective mono- and di-allylation and allenylation of chlorosilanes using indium

Allyl and allenyl groups have been introduced into silicon systems by the allylation and allenylation of chlorosilanes using allyl bromide or propargyl bromide with indium. The allylation of chlorosilanes afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. By applying this method, the reactions of 1-bromo-3-methylbut-2-ene, 3-bromo-2-methylprop-1-ene and 3-bromobut-1-ene with chlorosilanes also proceed smoothly to give regioselectively allylic rearrangement products in good yields. Mediated by indium, dichlorosilanes (R₂SiCl₂) and trichlorosilanes (RSiCl₃) can either afford monoallylated silanes or diallylated silanes depending on the amount of allyl bromide and indium used.     

Silver(I)‐Promoted Radical Sulfonylation of Allyl/Propargyl Alcohols: Efficient Synthesis of γ‐Keto Sulfones

An efficient Ag₂CO₃‐promoted sulfonylation of allyl/propargyl alcohols with sodium sulfinates has been developed. The reaction tolerates a wide range of functional groups to deliver γ‐keto sulfones in high yields (up to 93 %). Propargyl alcohols furnished trimerization product 1,3,5‐triaroylbenzenes in the presence of sodium methanesulfinate under the standard conditions. A mechanism involving a sulfonyl radical was suggested.     

Stereoselective,nonracemic synthesis of ω-borono-α-amino acids

ω-Unsaturated α-amino acids are synthesized through condensation of allyl and propargyl bromides or of 9-bromoundecene with a Ni(II) complex of the Schiff base derived from glycine and BPB. Hydroboration with Ipc₂BH followed by oxidation with acetaldehyde affords enantiomerically pure ω-borono-α-aminocarboxylic acids.     

Synthetic Reactions Using Low‐valent Titanium Reagents Derived from Ti(OR)4 or CpTiX3 (X = O‐i‐Pr or Cl) in the Presence of Me3SiCl and Mg

In the presence of Me₃SiCl, Ti(OR)₄ or CpTiX₃ (X = O‐i‐Pr or Cl) is reduced by Mg powder in THF to gradually generate a specific low‐valent titanium (LVT) species that mediates several synthetic reactions. The LVT‐catalyzed C–O bond‐cleaving reactions of allyl and propargyl ethers and esters generate parent alcohols and carboxylic acids, respectively. O‐allyl and propargyl carbamates are also readily deprotected by the LVT to afford parent amines. In addition, the respective reductive N–S or O–S bond cleavage of sulfonamides or sulfonyl esters mediated by the LVT was developed as a novel facile deprotection method. The reagent catalyzes intra‐ and intermolecular alkyne or alkyne/nitrile cycloaddition to produce substituted benzenes and pyridines, while epoxides and oxetanes are reduced to alcohols via an LVT‐mediated homolytic ring opening. The McMurry coupling of aryl aldehydes and ketones proceeds with the LVT under homogeneous and mild reaction conditions and is effective for the polymerization of aromatic dialdehydes, generating conjugated polymers. Finally, imino‐pinacol coupling of imines is mediated by the LVT to provide 1,2‐diamines.     

Allylstannation: VII. Preparation of carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl esters by transalkoxylation of 4-n-dibutylchlorostannoxy-1-alkenes and 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides

Carboxylic acid 1-alkene-4-yl and 1-alkyne-4-yl, esters (RCH(CH₂CHCH₂)OCOR′ ad RCH(CH₂CCH)OCOR′, R = R′ or R ≠ R′ = alkyl or alkenyl group) can be readily prepared in high yields by transalkoxylation reactions between 4-n-dibutylchlorostannoxy-1-alkenes or 4-n-dibutylchlorostannoxy-1-alkynes with acyl chlorides. This represents a general route for preparation of esters containing allyl or propargyl groups.     

O-Alkylation of furan and thiophene ketoximes in conditions of interphase catalysis in a liquid/solid system

Alkylation of 2 furanyl- and 2-thienylalkyl ketoximes with alkyl, allyl, and propargyl halides in the two phase catalytic system sol. K₂CO₃/C₆H₆/18-crown-6 at room temperature causes the formation of mixtures of E- and Z-isomers of the corresponding O-ethers with yields of 32–74%. Partial E/Z-isomerization takes place during the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 18–23, January, 1994.     

7α-alkylation, 7,7-bisalkylation,and reduction of the 20-oxo group of poststerone in reactions with alkyl halides in lithium–ammonia solution

Reactions of poststerone with methyl iodide, allyl bromide, and propargyl bromide in lithium–ammonia solution resulted in its completely stereoselective 7α-alkylation accompanied by reduction of the 20-oxo group with formation of equimolar amounts of 20R- and 20S-hydroxy derivatives. The reaction of poststerone with excess allyl bromide afforded 7,7-bis-allyl 20R- and 20S-alcohols at a ratio of 3: 1. The reduction of the 20-oxo group in the alkylation of poststerone with excess propargyl bromide led to the formation of an equimolar mixture of Δ⁸⁽¹⁴⁾- and Δ⁸⁽⁹⁾-isomers with exclusive S configuration of C²⁰.     

二价钌催化的金属卡宾经由的硫叶立德[2,3]-σ重排反应研究

报道烯(炔)基硫醚与α-重氮羰基化合物, 在[RuCl₂(p-cymene)]₂催化下, 经由金属卡宾发生硫叶立德[2,3]-σ重排反应(Doyle-Kirmse反应). 在Ru(II)作用下, α-重氮羰基化合物与烯丙基硫醚的反应以较好收率生成相应的[2,3]-σ重排产物高烯丙基硫醚. 同样条件下与炔丙基硫醚的反应则生成[2,3]-σ重排产物联烯和呋喃衍生物, 后者是联烯进一步在Ru(II)作用下重排的产物.     

Reactions of a Ruthenium Complex with Substituted N‐Propargyl Pyrroles

In an investigation into the chemical reactions of N‐propargyl pyrroles 1 a – c , containing aldehyde, keto, and ester groups on the pyrrole ring, with [Ru]?Cl ([Ru]=Cp(PPh₃)₂Ru; Cp=C₅H₅), an aldehyde group in the pyrrole ring is found to play a crucial role in stimulating the cyclization reaction. The reaction of 1 a , containing an aldehyde group, with [Ru]?Cl in the presence of NH₄PF₆ yields the vinylidene complex 2 a , which further reacts with allyl amine to give the carbene complex 6 a with a pyrrolizine group. However, if 1 a is first reacted with allyl amine to yield the iminenyne 8 a , then the reaction of 8 a with [Ru]?Cl in the presence of NH₄PF₆ yields the ruthenium complex 9 a , containing a cationic pyrrolopyrazinium group, which has been fully characterized by XRD analysis. These results can be adequately explained by coordination of the triple bond of the propargyl group to the ruthenium metal center first, followed by two processes, that is, formation of a vinylidene intermediate or direct nucleophilic attack. Additionally, the deprotonation of 2 a by R₄NOH yields the neutral acetylide complex 3 a . In the presence of NH₄PF₆, the attempted alkylation of 3 a resulted in the formation the Fischer‐type amino–carbene complex 5 a as a result of the presence of NH₃, which served as a nucleophile. With KPF₆, the alkylation of 3 a with ethyl and benzyl bromoacetates afforded the disubstituted vinylidene complexes 10 a and 11 a , containing ester groups, which underwent deprotonation reactions to give the furyl complexes 12 a and 13 a , respectively. For 13 a , containing an O‐benzyl group, subsequent 1,3‐migration of the benzyl group was observed to yield product 14 a with a lactone unit. Similar reactivity was not observed for the corresponding N‐propargyl pyrroles 1 b and 1 c , which contained keto and ester groups, respectively, on the pyrrole ring.