Lithium acetylides as alkynylating reagents for the enantioselective alkynylation of ketones catalyzed by lithium binaphtholate

Chiral lithium binaphtholate effectively catalyzed the enantioselective alkynylation of ketones using lithium acetylide as an alkynylating agent. This is the first example of the catalytic enantioselective addition of lithium acetylide to carbonyl compounds without the aid of other metal sources.     

Synthesis and Ritter Reaction of 2-Ethynyladamantan-2-ol

The reaction of adamantan-2-one with lithium acetylide gave 2-ethynyladamantan-2-ol. The latter reacted with acetonitrile in the presence of sulfuric acid through formation of an intermediate classical carbocation, leading to 2-acetylamino-2-ethynyladamantane and 1-acetylamino-2-acetyladamantane at a ratio of 20:1.     

Stereoselective synthesis of secondary and tertiary propargylic alcohols induced by a chiral sulfoxide auxiliary

The synthesis of optically active secondary and tertiary propargylic alcohols was accomplished by addition of lithium acetylide to chiral β-sulfinyl enones. Only a stoichiometric amount of the lithium acetylide was required and various substituents were tolerated. This reaction could be applied to substrates consisting of both ketones and aldehydes in high yields and excellent diastereoselectivities.     

Mechanism of acylation of lithium phenylacetylide with a Weinreb amide

Additions of lithium phenylacetylide to a Weinreb amide are described. Dimeric lithium acetylide reacts via a monosolvated monomer-based transition structure. The robust tetrahedral intermediate forms sequentially a C(1) 2:2 mixed tetramer with the excess lithium acetylide and a 1:3 (alkoxide-rich) mixed tetramer. The stabilities of the mixed tetramers are consistent with a pronounced autoinhibition.     

Electronic effect on the regioselectivity in the ring opening of para-substituted phenyloxiranes by acetylides

The electronic effect on the regioselectivity in the alkynylation of phenyloxiranes was investigated using three kinds of metal acetylides. BF₃ mediated lithium acetylide provided either the α- or β-alkynylated products by controlling the effect of the para-substituents of the phenyloxiranes. LiClO₄ mediated lithium acetylide and titanium acetylide, on the other hand, afforded predominantly the β- and α-products, respectively.     

Synthesis of mono- and diarylacetylenes

Arylacetylenes have been synthesized by CC coupling of lithium acetylide with aryl bromide in the presence of a palladium(0) catalyst.     

Building from Ga‐Porphyrins: Synthesis of Ga‐Acetylide Complexes Using Acetylenes and Polyynes

Multidimensional, conjugated building blocks have been formed through the axial coordination of polyynes to the central Ga atom of tetraarylporphyrins. Electron deficient pentafluorophenyl substituents in the meso‐positions provide more stable σ‐acetylide complexes to Ga than analogous structures with tert‐butylphenyl groups. Mono‐, di‐, and triynes have been used, including a pyridyl endcapped diyne that allows for formation of porphyrin triads through coordination of the pyridyl ligand to a Ru porphyrin.     

Polyyne synthesis using carbene/carbenoid rearrangements

Rearrangement of a carbene/carbenoid intermediate to form an acetylene moiety, known as the Fritsch-Buttenberg-Wiechell (FBW) rearrangement, was developed for the formation of polyynes and polyyne frameworks within highly conjugated organic materials. Necessary precursors can be prepared through formation of an alkynyl ketone, followed by dibromoolefination under Corey-Fuchs conditions. The carbenoid rearrangement is brought about by treatment of the dibromoolefin with BuLi under mild conditions. The success of these FBW reactions is quite solvent-dependent, and nonpolar hydrocarbon solvents (e.g., hexanes, toluene, benzene) work quite well, while use of ethereal solvents such as diethyl ether and tetrahydrofuran (THF) does not provide the desired polyyne product. This protocol was successfully applied to the formation of silyl, alkyl, alkenyl, and aryl polyynes, including di-, tri-, and tetrayne products, as well as the construction of two-dimensional carbon-rich molecules. A one-pot variant of this procedure is being developed and is particularly applicable toward the synthesis of polyyne natural products. Formation of a series of triisopropylsilyl end-capped polyynes, from the triyne to decayne, was achieved. Third-order nonlinear optical properties of these polyynes were evaluated. This study shows that the molecular second hyperpolarizabilities for the polyynes as a function of length increase at a rate that is higher than all other nonaromatic organic oligomers.     

Synthesis of conjugated enynes from ketones and aldehydes by 1,2-CC insertion and 1,2-CH insertion of carbenoids as the key reactions

The addition reactions of 1-chlorovinyl p-tolyl sulfoxides, which were derived from ketones and chloromethyl p-tolyl sulfoxide, with lithium acetylides gave adducts in moderate to good yields. Treatment of the adducts with Grignard reagents resulted in the formation of conjugated enynes in good to high yields via the 1,2-carbon-carbon insertion (1,2-CC insertion) reaction of the generated magnesium carbenoid intermediates. On the other hand, the addition reactions of 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes with lithium acetylides directly gave conjugated enynes bearing a p-tolyl sulfinyl group at the 1-position through the 1,2-carbon-hydrogen insertion (1,2-CH insertion) reaction of the generated lithium carbenoid intermediates. These procedures provide a good way for the synthesis of multi-substituted conjugated enynes from ketones and aldehydes.     

Sulfonyl-stabilized oxiranyllithium-based approach to polycyclic ethers. Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin

Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin, marine polycyclic ether toxins causative of diarrheic shellfish poisoning, has been accomplished. The A-ring fragment was constructed by coupling of an appropriately functionalized sulfonyl-stabilized oxiranyl anion and a triflate prepared from an erythritol derivative. An iterative protocol of the oxiranyl anion strategy was also applied for the construction of the DEF-ring fragment. The triflate derivatives of the A-ring and the DEF-ring fragments were connected with lithium acetylide. The resulting acetylene derivative was further transformed into the hexacyclic ABCDEF fragment via oxidation of the acetylene unit to 1,2-diketone, double methyl acetal formation, and reductive etherification.     

Enhanced solid-state metathesis routes to carbon nanotubes

Ignition of three solids creates multiwalled carbon nanotubes in seconds. A solid-state metathesis (exchange) reaction between hexachloroethane (C2Cl6) and lithium acetylide (Li2C2) with 5% cobalt dichloride (CoCl2) added as an initiator produces up to 7% carbon nanotubes, as observed via transmission electron microscopy. Using the concept that sulfur can promote nanotube growth, the reaction yield can be increased to 15% by switching to CoS as the initiator. The more readily available, inexpensive calcium carbide (CaC2) can be substituted for lithium acetylide while maintaining comparable yields. Switching initiators to FeS can be used to further enhance the yield. A systematic study of the C2Cl6/CaC2 reaction system indicates that a yield up to 25% can be realized by using 6% FeS as the initiator. Reaction temperatures for the C(2)Cl6/CaC2 system of up to 3550 degrees C are calculated using thermodynamic data assuming quantitative yield and adiabatic conditions.     

Design and Preparation of Platinum–Acetylide Organogelators Containing Ethynyl–Pyrene Moieties as the Main Skeleton

A series of new platinum‐acetylide complexes containing ethynyl‐pyrene moieties as the main skeleton were synthesized and characterized. The investigation of the absorption and emission spectra of these complexes revealed that the extension of the molecular size with the introduction of different numbered platinum‐acetylide fragments can efficiently tune the absorption and emission bands from the UV to the longer wavelength region. Moreover, the gelation properties of these complexes were investigated by the “stable‐to‐inversion‐of‐a‐test‐tube” method. Most newly designed platinum‐acetylide compounds presented a stable gel‐formation property in some of the tested solvents. The morphology of the xerogels was investigated by scanning electron microscopy (SEM). Furthermore, the concentration‐ and temperature‐dependent absorption and emission properties of these complexes were investigated, which support the formation of J‐type assemblies during the aggregation process. More importantly, it was found that the complexes 4 a‐C6 , 4 a , and 4 a‐C18 with four platinum‐acetylide fragments presented potential applications as luminescent organometallic gels.     

Total synthesis of microcarpalide

[reaction: see text] An efficient, convergent approach for the total synthesis of microcarpalide (1) is described. The synthetic strategy features the Sharpless asymmetric dihydroxylation, regioselective epoxide opening with various nucleophiles such as a lithium acetylide and cuprates derived from the vinyl stannane and the vinyl iodide for the construction of a C7-C8 trans-double bond and Yamaguchi macrolactonization as the key steps.     

Die Umsetzung von Vinylbromid und substituierten Vinylbromiden mit Lithium in Tetrahydrofuran zu Lithiumacetyliden

Zusammenfassung Bei der Umsetzung mit metallischem Li in sied. Tetrahydrofuran (THF) entstehen aus 2-Brom-propen und 2-Brom-buten-(1) an Stelle der erwarteten Lithiumalkenyle die Acetylide R-CCLi, wobei allerdings ein größerer Teil des Ausgangsbromids in das entsprechende Alken übergeht. Außerdem wird neben LiBr auch noch eine geringe Menge LiH gebildet, das bei, der analogen, zu C₂Li₂ führenden Umsetzung des Vinylbromids in wesentlich größerer Menge entsteht. Die Bildung von Lithiumvinyl konnte nicht beobachtet werden. Auchcis-1-Brom-buten-(1), geht inTHF in das entsprechende Lithiumacetylid über.InTHF, das die zu Acetylid führenden Reaktionen offenbar begünstigt, wird schon bei—65° Acetylidbildung aus 2-Brompropen beobachtet, in Äther aber nur dann, wenn bei Siedetemp. und in höherer Konzentration als bei der Darstellung der Lithiumalkenyle bisher üblich gearbeitet wird.Die Acetylide, deren Bildungsmechanismus diskutiert wird, werden mit verschiedenen Ketonen umgesetzt.Phenylacetylen und Octin-(1) geben mit metall. Li in sied.THF die entsprechenden Acetylide. Der dabei verfügbar werdende Wasserstoff führt einen Teil der Ausgangsverbindungen in Äthylbenzol bzw. Octen-(1) über; LiH oder Wasserstoff entsteht dabei nicht. Acetylen selbst greift unter diesen Bedingungen Li nur oberflächlich an.Reaction of metallic lithium with 2-bromo-propene and 2-bromo-but-1-ene in boiling tetrahydrofurane yields acetylides of the structure R–CC-Li instead of the expected lithium alkenes. To a larger extent, however, the starting material is converted to the corresponding alkene. Besides LiBr a small amount of LiH is formed. In the analogous reaction with vinyl bromide leading to C₂Li₂ an essentially larger amount of LiH is formed, whereas the formation of lithium vinyl was not observed.cis-1-Bromo-but-1-ene inTHF similarily gives the corresponding lithium acetylide.THF obviously favours the reactions leading to acetylides, e.g. at—65°C formation of the acetylide from 2-bromo-propene can be observed. In diethyl ether however formation of acetylides requires, reflux temperature and concentrations higher as usual for the preparation of lithium-alkenyles.The mechanism of the acetylide formation as well as the reaction of the acetylides with certain ketones are described. On treatment of phenylacetylene and octine-1 with metallic lithium in boilingTHF the corresponding acetylides are obtained. Some of the starting material is converted into ethylbenzene and octene-1 respectivly. LiH or H₂ are not formed. Under the same conditions lithium is only slightly affected by acetylene.Dem verehrten Kollegen Professor Dr. Dr. h. c.F. Wessely zum 70. Geburtstag in Freundschaft gewidmet.     

Diastereoselective alkynylation of N-p-tolylsulfinylimines with aluminum acetylides

The addition of alkynyl dimethyl aluminum compounds onto N-p-tolylsulfinylimines was investigated. The reaction was proved to be totally regioselective, leading to propargylamines with high diastereoselectivity (up to 99% de). Addition of aluminum derivatives gave a reversal of diastereoselectivity compared to the addition reaction of lithium acetylide.     

Synthesis of N-methoxy-N-methyl-beta-enaminoketoesters: new synthetic precursors for the regioselective synthesis of heterocyclic compounds

[Structure: see text] Weinreb amides react with the lithium or sodium acetylide of ethyl propynoate in a hitherto unexplored acyl substitution-conjugate addition sequence to furnish (E)-N-methoxy-N-methyl-beta-enaminoketoesters. This approach provides a diverse entry to densely functionalized heterocyclic compounds, including pyrazoles through regioselective cyclocondensations with hydrazines in a microwave-assisted reaction.     

Synthesis of substituted acetylenic epoxides followed by indium-catalyzed rearrangement to 2,3,5-trisubstituted furans

Syntheses of various aromatic and aliphatic 2,3,5-trisubstituted furans from acetylenic epoxides are described. These epoxides are directly prepared by nucleophilic ring closure of propargylic alkoxides generated by lithium acetylide addition to α-haloketones.     

Efficient domino process based on the catalytic generation of non-metalated,conjugated acetylides in the presence of aldehydes or activated ketones

The extremely mild and highly efficient catalytic generation of non-metalated, conjugated acetylides is reported. These acetylides are used to generate enol-protected functionalized propargylic alcohols 1, 1,3-dioxolane compounds 2, or 3,4,5-trisubstituted 4,5-dihydrofurans 4 through serial multibond-forming processes. The method calls for a nucleophile (a tertiary amine or phosphine) as a chemical activator, a conjugated terminal acetylene as the acetylide source, and an aldehyde or activated ketone as the electrophilic partner. The chemical outcome of this process depends on the nature of the nucleophile, the temperature, stoichiometry and solvent, and it can be tailored selectively by the appropriate choice of the experimental conditions.     

An elaborate route of exclusive sonogashira polycondensation to alternating BODIPY–porphyrin ethynylene‐conjugated polymer

The first synthesis of the fully conjugated ethynylene‐linked polymer incorporating boron dipyrrine complex (BODIPY) and zinc porphyrin in the main chain was performed based on the exclusive Sonogashira polycondensation. Comprehensive experimental and theoretical investigations lead to an elaborate synthetic route to circumvent the possible side reactions of BODIPY in the presence of the palladium catalyst. Additionally, optimization of the synthetic conditions found that dichloromethane as the solvent suppresses the formation of the pseudo‐trans dimer of the copper acetylide and mitigates the undesired oxidative homocoupling reaction. Eventually, the exclusive Sonogashira polycondensation in dichloromethane provided the alternating BODIPY–porphyrin ethynylene‐conjugated polymer, which displayed absorption up to the near‐infrared wavelengths. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2457–2465     

A novel low‐bandgap conjugated polymer based on Ru(II) bis(acetylide) complex and BODIPY moieties

A novel conjugated polymer P‐1 incorporating Ru(II) bis(acetylide) complex and borondipyrromethene (BODIPY) moieties in the main chain was synthesized by Pd‐catalyzed Sonogashira coupling reaction of diethynyl substituted BODIPY derivative ( M‐1 ) and Ru(II) bis(acetylide) complex ( M‐2 ), and the reference polymer P‐2 was obtained from the same method as preparation of P‐1 . Compared with P‐2 , Ru(II)‐containing polymer P‐1 shows low‐bandgap as 0.87 eV from cyclic voltammetry, and obvious redshifts in both UV–vis absorption and fluorescence spectra. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1686–1692