联二烯丁基硫醚衍生物合成呋喃的反应

本文报道以联二烯丁基硫醚为起始物的呋喃衍生物的合成方法.实验结果表明,β-联二烯丁基硫醚醇在氢化钠的作用下以很高的收率环化生成一个苯硫基离去的呋喃产物,β-联二烯丁基硫醚醛与外加亲核试剂作用后能得到多一个取代的类似呋喃产物,而β-联二烯丁基硫醚酮在P2O5的促进下也能环化生成呋喃衍生物.     

Synthesis of furan from allenic sulfide derivatives

In this paper, we report the synthesis of furan derivatives from allenic sulfides. By the reaction with NaH, β-Hydroxyl allenic sulfides were found to generate furan products in excellent yields with the removal of phenylthio group. β-Aldehyde allenic sulfides were found to give similar furan products with one more substituent when treated with additional nucleophilic reagents. β-ketone allenic sulfides can also cyclize to give furan derivatives with the promotion of P₂O₅.     

Unusual

All-carbon 1,3-dipoles derived from allenic esters/ketones, by catalytic interaction with triphenylphosphine, undergo an unusual [8 + 2] annelation with tropone, leading to 8-oxa-9-(ethoxycarbonyl/acylalkylidene)bicyclo[5.3.0]deca-1,3,5-trienes. Dipoles derived from allenic ketones as well as an alpha-methyl-substituted allenic ester display high reactivity and selectivity.     

Intramolecular Diels-Alder reactions of optically active allenic ketones: chirality transfer in the preparation of substituted oxa-bridged octalones

The intramolecular Diels-Alder reaction of allenic ketones containing a furyl unit (IMDAF) to generate oxatricyclic systems in good yields is described. The alkene dienophiles 1ab give poor yields of the cycloadducts 2ab, presumably due to the facile retro Diels-Alder reaction. However, the analogous allenic dienophile 7 afforded the desired cycloadduct 8 in 91% yield on treatment with dimethylaluminum chloride. When the allene bears an alkyl substituent on the terminal carbon, complete diastereoselectivity is seen in the IMDAF, e.g. cyclization of 14 gave only the cycloadduct 15 in 80% yield presumably due to greater steric hindrance in the transition state II as compared to that in I. Finally we report complete chirality transfer of the stereochemistry of an allene to the carbon framework of the oxatricyclic system. Thus, the optically active allenic ketone 20 afforded only the desired cycloadduct 21 with the correct absolute stereochemistry needed for the synthesis of the arisugacin class of natural products.     

Preparation of propargyl hydroperoxides by regioselective oxidation of allenic zinc reagents with molecular oxygen

Treatment of allenic zinc reagents (R(1)R(2)C[double bond]C[double bond]C(R(3))ZnL), generated by the reaction of propargyl derivative (R(1)R(2)C(X)[triple bond](CH) with triorganozincates (R(3)(3)ZnLi), under oxygen atmosphere in the presence of ZnCl(2) and chlorotrimethylsilane afforded propargyl hydroperoxides (R(1)R(2)C(OOH)C[triple bond];CR(3)) regioselectively. In this reaction, the use of ZnCl(2) and chlorotrimethylsilane as additives is essential for the transformation of the initially generated allenic reagents to more reactive chlorozinc species.     

Synthesis of novel enantiopure 4-hydroxypipecolic acid derivatives with a bicyclic beta-lactam structure from a common 3-azido-4-oxoazetidine-2-carbaldehyde precursor

Two different stereocontrolled accesses to new 4-hydroxypipecolic acid analogues with a bicyclic beta-lactam structure have been developed by using intramolecular reductive amination or allenic hydroamination reactions in 2-azetidinone-tethered azides. The access to the cyclization precursors was achieved from 3-azido-4-oxoazetidine-2-carbaldehyde via metal-mediated carbonyl-allenylation in aqueous environment or by organocatalytic direct aldol reaction. The tin hydride-promoted cyclization of the 2-azetidinone-tethered azidoallene is totally regioselective for the central allenic carbon providing a fused piperidine.     

Spectres de masse de composes alleniques—I : Transposition de type McLafferty de groupes heteroatomiques et de phenyle sur le carbone allenique central

Mass spectra of allenic compounds substituted with a hydrocarbon chain bearing a heteroatomic group (hydroxy, alcoxy, halogen, dialkylamino) or a phenyl in the γ position exhibits a strong peak corresponding to the loss of C₂H₄ (28a.m.u.) from the molecular ion. This is commonly the base peak of the spectra and due to a McLafferty type transfer of the heteroatom or phenyl group to the central allenic carbon atom. The methyl group shows a lower migratory aptitude in such a process. This type of fragmentation involving the migration of heteroatomic groups is not observed in the spectra of γ-halogen and γ-hydroxyketones, alkenes, alkynes or arenes and seems to be characteristic of the allenic linkage. A nucleophilic attack by heteroatom group (or phenyl) on the central allenic carbon atom is proposed.     

Au-catalyzed cyclization of allenylsilanes. Regioselective conversion to 2-amino-4-silylmethylene γ-butyrolactone

The Au(I)-catalyzed cyclization of an allenylglycine, which possessed a silyl group attached to the opposite side of the allenic terminus, occurred at the allenic center to produce the 2-amino-4-silylmethylene-substituted γ-butyrolactone 2a in a highly regio- and stereoselective manner. The presence of a silyl group at the allenic terminus is crucial for the present 5-endo-dig γ-butyrolactonization.     

Ã-X absorption of propargyl peroxy radical (H-C≡C-CH2OO·): a cavity ring-down spectroscopic and computational study

The ?-X electronic absorption spectrum of propargyl peroxy radical has been recorded at room temperature by cavity ring-down spectroscopy. Electronic structure calculations predict two isomeric forms, acetylenic and allenic, with two stable conformers for each. The acetylenic trans conformer, with a band origin at 7631.8 ± 0.1 cm(-1), is definitively assigned on the basis of ab initio calculations and rotational simulations, and possible assignments for the acetylenic gauche and allenic trans forms are given. A fourth form, allenic cis, is not observed. Simulations based on calculated torsional potentials predict that the allenic trans form will have a long, poorly resolved progression in the OOCC torsional vibration, consistent with experimental observations.     

Indium-mediated regio- and chemoselective synthesis of alpha-hydroxyalkyl allenic esters and gold-catalyzed cyclizations to ethyl 2-naphthoate derivatives

The regio- and chemoselective synthetic method of functionalized alpha-hydroxyalkyl allenic esters was developed from the reactions of various aldehydes with organoindium reagent generated in situ from indium and ethyl 4-bromobutynoate. The alpha-hydroxyalkyl allenic esters possessing electron-donating groups were cyclized to ethyl 2-naphthoate derivatives through intramolecular C-alkylation catalyzed by gold salts.     

Synthesis of β-Enaminoesters and Lactams by Michael Addition of N-Benzylaniline to New Allenic Esters and Lactams

The synthesis of original allenic lactams 2 and allenic esters 5 is presented and their Michael condensation with N-benzylaniline described.     

Divergent Reactivity of Homologue ortho‐Allenylbenzaldehydes Controlled by the Tether Length: Chromone versus Chromene Formation

The divergent behavior of two homologue allenals, namely, 2‐(buta‐2,3‐dienyloxy)‐ and 2‐(propa‐1,2‐dienyloxy)benzaldehydes, as cyclization substrates is described. 2‐(Buta‐2,3‐dienyloxy)benzaldehydes suffers a formal allenic carbocyclization reaction to afford chromenes, whereas 2‐(propa‐1,2‐dienyloxy)benzaldehydes react to yield chromones. The formation of chromenes is strictly a formal hydroarylation process divided into two parts, namely, allenic Claisen‐type rearrangement and oxycyclization. An unknown N‐heterocyclic carbene (NHC)‐catalyzed allenic hydroacylation reaction must be invoked to account for the preparation of chromones. ortho‐Allenylbenzaldehydes bearing either electron‐donating substituents or electron‐withdrawing substituents worked well to afford both the hydroarylation and hydroacylation products. This unexpected difference in reactivity can be rationalized by means of density functional theory calculations.     

Design,Synthesis, Evaluation and Structure of Allenic 1α,25-Dihydroxyvitamin D3 Analogs with Locked Mobility at C-17

Vitamin D receptor ligands have potential for the treatment of hyperproliferative diseases and disorders related to the immune system. However, hypercalcemic effects limit their therapeutical uses and call for the development of tissue-selective new analogs. We have designed and synthesized the first examples of 1α,25-dihydroxyvitamin D₃ analogs bearing an allenic unit attached to the D ring to restrict the side-chain conformational mobility. The triene system was constructed by a Pd⁰-mediated cyclization/Suzuki-Miyaura cross-coupling process in the presence of an allenic side chain. The allenic moiety was built through an orthoester-Claisen rearrangement of a propargylic alcohol. The biological activity and structure of (22S)-1α,25-dihydroxy-17,20-dien-24-homo-21-nor-vitamin D₃ bound to binding domain of the vitamin D receptor, provide information concerning side-chain conformational requirements for biological activity.     

Regio- and stereocontrolled dimerisation of allenic alcohols via introduction of an acetoxy group using ruthenium catalysis

Acetate-introduced dimers of allenes can be produced from the ruthenium catalysed reaction of allenic alcohols with AcOH. Incorporation of acetate component is activated in the presence of Cu(OAc)₂ and amine, and various allenic alcohols can be transformed to the corresponding dimers in a regio- and stereoselective manner.     

Transposition bis-homoallénylique: solvolyse de γ-tosylates alléniques

Cyclisation (formation of derivatives of 2-methylidene-cyclopentanol or cyclohexanone) with inversion of configuration and retention of optical activity is observed during the solvolysis of secondary γ-allenic tosylates. Steric factors rather than electronic ones control the participation of one of the double bonds in the allenic system. Kinetic results and product distribution are discussed.     

C-H amination/cyclocarbonylation of allene carbamates: a versatile platform for the synthesis of α,β-unsaturated γ-lactams

Despite their utility as building blocks for the construction of a variety of nitrogen-containing heterocyclic scaffolds, the preparation of allenic amines 2 via the direct C-H amination of allenes of the general structure 1 has not been well-explored. In this report, we describe our preliminary studies on the factors that control the chemoselectivity of Rh-catalyzed aminations of allenes to give either bicyclic methylene aziridines or the desired allenic amines 2. Additionally, the conversion of selected allenic amines to α,β-unsaturated γ-lactam scaffolds via a facile Ru₃(CO)₁₂ catalyzed cyclocarbonylation is described.     

A simple approach to separate a mixture of homopropargylic and allenic alcohols

A simple and practical approach to separate homopropargylic alcohol from allenic alcohol has been developed. It involves the formation of an insoluble silver acetylide species between silver nitrate and homopropargylic alcohol in aqueous acetone which can be separated from the allenic alcohol through a simple filtration. The homopropargylic alcohol can subsequently be recovered by hydrolysis with 1 N HCl. This protocol has been applied to the separation of a mixture of chiral homopropargylic and allenic alcohols in excellent yields with retention of absolute stereochemistry.     

Réaction de quelques allènes avec l'hydrure de di-isobutyl-aluminium

Reduction of the more substituted of the two double bonds of the allenic linkage can be selectively achieved by the reaction with DIBAH followed by hydrolysis.     

On the reaction of metallated acetylenes and allenes with carbon disulfide. Influence of the alkali metal counter-ion and the substituents in the acetylene and allene on the course of the reaction

Addition at low temperatures of carbon disulfide to a solution of the lithium compound

(R¹ = CH₃, C₃H₇, Ph, OCH₃, SCH₃) results in the initial formation of an allenic carbodithioate H₂CCC(R¹)CSSLi, while for R¹ = t-C₄H₉ or SiMe₃ acetylenic carbodithioates R¹CCCH₂CSSLi are formed. The initial products undergo very rapid subsequent reactions. For R¹ = CH₃ or C₃H₇ the lithium compound adds (in the allenic form) in a conjugated fashion to the CCCS system of the allenic carbodithioate. The acetylenic dithioates are deprotonated to give the geminal dithiolates R¹CCCHC(SLi)₂. For R¹ = Ph, OCH₃ or SCH₃, subsequent deprotonation at the terminal carbon atom of the initial allenic dithioate gives enyne dithiolates HCCC(R¹)C(SCH₃)₂; this reaction proceeds more satisfactorily with the potassium compounds.