Room temperature Fe(NO3)3·9H2O/TEMPO/NaCl-catalyzed aerobic oxidation of homopropargylic alcohols

A practical and eco-friendly aerobic oxidation of homopropargylic alcohols using Fe(NO₃)₃·9H₂O/TEMPO/NaCl as catalysts at room temperature under atmospheric pressure was developed affording corresponding homopropargylic ketones with moderate to good yields. Aryl, heteroaryl as well as alkyl 1,2-allenic ketones were obtained by the isomerization of corresponding terminal homopropargylic ketones through column chromatographic workup on silica gel.     

Highly selective formation of propargyl- and allenyltrichlorosilanes and their regiospecific addition to various types of aldehydes: preparation of both allenic and homopropargylic alcohols

The highly selective preparation of propargyl- and allenyltrichlorosilanes via metal-catalyzed silylation of propargyl chloride has been developed. These trichlorosilyl nucleophiles were then shown to add to various types of aldehydes to afford the corresponding allenic and homopropargylic alcohols, respectively, in high yields with complete regiospecificity. Remarkably, these carbon–carbon bond-forming reactions simply proceeded in N,N-dimethylformamide (DMF) without using any metal catalysts.     

TMSI mediated Prins-type cyclization of ketones with homoallylic and homopropargylic alcohol: synthesis of 2,2-disubstituted-, spirocyclic-4-iodo-tetrahydropyrans and 5,6-dihydro-2H-pyrans

The Prins-type cyclization of ketones with homoallylic and homopropargylic alcohols in the presence of TMSI generated in situ from TMSCl and NaI produced 2,2-disubstituted- or spirocyclic-4-iodo-tetrahydropyrans and spirocyclic-4-iodo-5,6-dihydro-2H-pyrans in good yields. These iodopyrans are reported for the first time.     

The silylalkyne-Prins cyclization: a novel synthesis of 4-iododihydropyrans

The silylated secondary homopropargylic alcohols undergo smooth coupling with aldehydes in the presence of molecular iodine under mild reaction conditions to produce 4-iododihydropyrans in good yields. This method is highly stereoselective, affording cis-dihydropyrans exclusively.     

Facile approach towards the synthesis of homochiral functionalised alcohols from 4-O-[(tert)-butyldimethylsilyl]-2,3-O-cyclohexylidene-l-threose of (l)-(+)-tartaric acid origin

(l)-(+)-Diethyl tartarate 2 has been transformed into the aldehyde 6. Grignard additions to 6 take place with moderate diastereoselectivity giving predominant formation of the anti products 8a–e. However, in each case the diastereoalcohols are easily separable by column chromatography giving rise to the formation of a series of functionalised homochiral alcohols 7 and 8. On the other hand Zn mediated allylation and propargylation of 6 in the presence of water proceeded efficiently with almost absolute (>99%) stereoselective formation of versatile functionalised homoallylic 8d and homopropargylic 8e alcohols respectively.     

Copper‐Catalyzed One‐Pot Trifluoromethylation/Aryl Migration/Carbonyl Formation with Homopropargylic Alcohols

A novel copper‐catalyzed one‐pot functionalization of homopropargylic alcohols that involves trifluoromethylation, aryl migration, and formation of a carbonyl moiety has been developed. This reaction constitutes the first direct conversion of homopropargylic alcohols into CF₃‐containing 3‐butenal or 3‐buten‐1‐one derivatives in a regioselective manner. Mechanistic studies indicate that the 1,4‐aryl migration proceeds through a radical pathway.     

Diastereoselective synthesis of enantioenriched homopropargyl amino alcohols from α-dibenzylamino aldehydes and their use as chiral synthons

Homochiral α-dibenzylamino aldehydes, prepared from the corresponding α-amino acids, react with propargyl bromide and zinc in DMF/THF (1:1) or DMF/Et₂O (1:1) at 20 °C to afford, in good yields and dr, homopropargylic 1,2-amino alcohols. anti Diastereomers were always formed as major products in this reaction. These compounds are versatile intermediates for a variety of synthetic targets: γ-amino-β-hydroxy-ketones, 4-amino-1,3-diols, 1,7-diamino-2,6-diols, and ω-amino-δ-hydroxy esters.     

Indium-mediated reaction of trialkylsilyl propargyl bromide with aldehydes: highly regioselective synthesis of allenic and homopropargylic alcohols

High regioselective preparation of either the allenic alcohols or homopropargylic alcohols using the indium-mediated reaction of trialkylsilyl propargyl bromides with various aldehydes has been accomplished. By just changing the silyl groups and the reaction conditions, both the allenic and homopropargylic alcohols can be obtained in high regioselectivities.     

Synthesis of lactones by intramolecular addition of alkoxythiocarbonyl free radicals to acetylenes

Lactones are obtained by treating dithiocarbonates of homopropargylic or homoallylic alcohols with n-Bu³SnH-Et₃B.     

Rh‐Catalyzed Reaction of Propargylic Alcohols with Aryl Boronic Acids–Switch from β‐OH Elimination to Protodemetalation

It is known that Rh‐catalyzed reaction of propargylic alcohols with aryl metallic reagents undergoes S_N2’‐type reaction affording allenes via a sequential arylmetalation and β‐OH elimination process. Here we report a Rh/Ag‐cocatalyzed reaction of propargylic alcohols with organoboronic acids affording stereo‐defined (E)‐3‐arylallylic alcohols via arylmetalation and protodemetalation with a high regio‐ and stereoselectivity under very mild conditions. The reaction exhibits a good substrate scope and the compatibility with synthetically useful functional groups with no racemization for optically active propargylic alcohols. Such a reaction may also be extended to homopropargylic alcohols with a remarkable regioselectivity and exclusive E‐stereoselectivity.     

Silicon-assisted propargylic transfer to aldehydes

A new and efficient method of obtaining homopropargylic alcohols via homopropargylic transfer from the allenic alcohol to various aldehydes in the presence of Lewis acid catalysts is described; stereochemical studies have shown that this process is the first oxonium [3,3]-sigmatropic rearrangement of an allenic alcohol to a homopropargylic alcohol in the presence of aldehydes and Lewis acid.     

Reaction du trimethyl chlorosilane avec les alcools α-cyclopropaniques en presence ou en l'absence d'halogenures de lithium.

α-Cyclopropyl alcohols react with Me₃SiCl, eventually in the presence of LiBr or LiI, leading to a cyclopropyl halide or (and) to a homopropargylic halide, according to the nature of the alcohol.     

Directed hydrozirconation of homopropargylic alcohols

Homopropargylic alcohols undergo directed hydrozirconation with Schwartz reagent (Cp₂ZrHCl) to generate vinyl-metal species in which the metal fragment is proximal to the alkoxide. Electrophilic trapping yields tri-substituted olefins in good yields with good control of regio- and stereochemistry. Experiments with a homopropargylic ether confirmed the role of the hydroxyl group in the directed hydrometalation.     

镝促进下醛、酮与炔丙基溴及苯基炔丙基溴的高 选择性反应

在金属镝的促进下,醛、酮可与炔丙基溴反应,高选择性高产率地得到相应的高炔丙醇,没有发现连二烯醇的存在。当用苯基炔丙基溴代替炔丙基溴与醛、酮反应时,主要得到了相应的连二烯醇,而没有发现高炔丙醇的存在,由此提出了六元环过渡态的反应机理。     

Synthése d'alcools α-alléniques par réaction d'organochromiques propargyliques sur les aldéhydes et les cétones

Propargylic bromides can be condensed with aldehydes and ketones in the presence of Hiyama's reagent (2CrCl₃+LiAlH₄ in THF) leading to α-allenic alcohols, to homopropargylic alcohols or to the mixture of both of them. The selectivity (or specificity) of this reaction depends on the substitution of the propargylic bromide, on the structure of the ketone, and on the presence of HMPT in the reaction mixture. In many cases, the α-allenic alcohol has been specifically or very selectively obtained. The mechanism of the reaction and the influence of the various parameters are discussed.     

Synthesis and biological evaluation of (S)-4-aminoquinazoline alcohols

A simple synthetic method for the preparation of enantiomerically pure (S)-4-aminoquinazoline alcohols from (S)-quinazolinone alcohols by key steps including chlorination, nucleophilic ipso substitution, and deacetylation is presented. Mutagenic and antimutagenic properties of the (S)-4-aminoquinazoline alcohols were investigated by using Salmonella typhimurium TA1535, and Escherichia coli WP2uvrA tester strains at 0.01, 0.1, and 1 μg/plate concentrations. (S)-4-aminoquinazoline alcohols were found to be genotoxically safe at the tested concentrations. Among the tested (S)-4-aminoquinazoline alcohols, the best antimutagenic activity was obtained with a methyl derivative at 0.1 μg/plate dose.     

Catalytic asymmetric transfer hydrogenation of ketones using terpene-based chiral β-amino alcohols

Catalytic asymmetric transfer hydrogenations of aromatic alkyl ketones have been studied using [RuCl₂(p-cymeme)]₂ and terpene-based β-amino alcohols. The limonene derived amino alcohol, (1S,2S,4R)-1-methyl-4-(1-methylethenyl)-2-(methylamino)cyclohexanol gave the most promising results. Chiral secondary alcohols were obtained in good to excellent yields and moderate enantioselectivities (up to 71%).     

Diastereo- and regioselective palladium-indium bimetallic cyclisation-Barbier-type allylation cascades

A new diastereo-and regioselective Pd/In bimetallic cascade process which assembles three contiguous chiral centres is described. Pd(0)-catalysed cyclisation of aryl iodides onto proximate 1,3-dienes generates π-allylpalladium(II) species, transmetallation with indium and subsequent Barbier-type addition to aldehydes affords heterocyclic homoallylic alcohols.     

CO2‐Activation for γ‐Butyrolactones and Its Application in the Total Synthesis of (±)‐Heteroplexisolide E

An efficient nickel(0)‐catalyzed highly regio‐ and stereoselective hydrocarboxylation of homopropargylic alcohols with ZnEt₂ in the presence of CO₂ (1 atm, balloon) to synthesize α‐alkylidene‐γ‐butyrolactones is described. The catalyst is highly active and can be applied for the synthesis of (optically active) mono‐ or bicyclic α‐alkylidene‐γ‐butyrolactones with excellent regio‐ and stereoselectivity and good functional group tolerance. The potential of the reaction has been demonstrated in the first synthesis of (±)‐heteroplexisolide E.     

Halogenative kinetic resolution of β-amido alcohols: chiral BINAP-mediated SN2 displacement of hydroxy groups by chlorides with inversion of stereochemistry

A series of optically active cyclic trans-β-amido alcohols were obtained by the non-enzymatic kinetic resolution of the corresponding racemic amido alcohols using commercially available (S)-BINAP and NCS by S_N2 halogenation of the hydroxy group. The product, cis-β-amido chloride, was also obtained in optically active form with an inversion of stereochemistry.