Copper-catalyzed cycloisomerizations of 5-en-1-yn-3-ols

[reaction: see text] The Cu(I)-catalyzed cycloisomerization of tertiary 5-en-1-yn-3-ols with an 1,2-alkyl shift affords stereoselectively tri- and tetracyclic compounds of high molecular complexity. These results are in agreement with a mechanism in which the cyclopropanation precedes the rearrangement.     

PtCl 2-catalyzed cycloisomerizations of allenynes

The PtCl2-catalyzed cycloisomerization of allenyne systems has been examined. This process is a highly versatile tool for obtaining products that cannot be attainable with other metals. Simple adjustment of the allene or alkyne substitution can direct the reactivity in a selective manner and give birth to important carbocyclic frameworks (hydrindenes, cyclic vinylallenes, and trienes).     

3-甲基-1-戊烯-4-炔-3-醇的合成

以甲基乙烯酮为原料,用乙炔基格氏试剂对其加成,然后水解得到目标物3-甲基-1-戊烯-4-炔-3-醇。研究了温度对反应的影响,发现在25℃的反应温度下,目标化合物的气相色谱产率为50%,减压蒸馏纯化后收率为30%。目标产物用1HNMR、IR进行了表征。     

Enantioselective synthesis of (1E,3S)-1-iodoundec-1-en-5-yn-3-ol,the eicosanoid synthon

A synthesis of the title compound, the synthon for the constanolactones and other eicosanoids, has been developed from achiral starting compounds. The synthesis is based on the S-enantiodirected dihydroxylation of the double bond to introduce a chirality and on the use of conformational restriction of the triple bond (the latent Z-double bond) surroundings.     

Gas-phase reactions of NO3 and N2O5 with (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol ('leaf alcohol'), (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol

The night-time atmospheric chemistry of the biogenic volatile organic compounds (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol ('leaf alcohol'), (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol, has been studied at room temperature. Rate coefficients for reactions of the nitrate radical (NO(3)) with these stress-induced plant emissions were measured using the discharge-flow technique. We employed off-axis continuous-wave cavity-enhanced absorption spectroscopy (CEAS) for the detection of NO(3), which enabled us to work in excess of the hexenol compounds over NO(3). The rate coefficients determined were (2.93 +/- 0.58) x 10(-13) cm(3) molecule(-1) s(-1), (2.67 +/- 0.42) x 10(-13) cm(3) molecule(-1) s(-1), (4.43 +/- 0.91) x 10(-13) cm(3) molecule(-1) s(-1), (1.56 +/- 0.24) x 10(-13) cm(3) molecule(-1) s(-1), and (1.30 +/- 0.24) x 10(-13) cm(3) molecule(-1) s(-1) for (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol. The rate coefficient for the reaction of NO(3) with (Z)-hex-3-en-1-ol agrees with the single published determination of the rate coefficient using a relative method. The other rate coefficients have not been measured before and are compared to estimated values. Relative-rate studies were also performed, but required modification of the standard technique because N(2)O(5) (used as the source of NO(3)) itself reacts with the hexenols. We used varying excesses of NO(2) to determine simultaneously rate coefficients for reactions of NO(3) and N(2)O(5) with (E)-hex-3-en-1-ol of (5.2 +/- 1.8) x 10(-13) cm(3) molecule(-1) s(-1) and (3.1 +/- 2.3) x 10(-18) cm(3) molecule(-1) s(-1). Our new determinations suggest atmospheric lifetimes with respect to NO(3)-initiated oxidation of roughly 1-4 h for the hexenols, comparable with lifetimes estimated for the atmospheric degradation by OH and shorter lifetimes than for attack by O(3). Recent measurements of [N(2)O(5)] suggest that the gas-phase reactions of N(2)O(5) with unsaturated alcohols will not be of importance under usual atmospheric conditions, but they certainly can be in laboratory systems when determining rate coefficients.     

Dimerization of 3-methylpent-2-en-4-yn-1-ol by diels-alder reaction with cleavage of a carbon-carbon bond

In this study, it was found that in the thermal reaction of Z-3-methylpent-2-en-4-yn-1-ol, two parallel processes occur — radical polymerization and formation of low-molecular-weight products by a nonradical pathway. The structure of the principal low-molecular-weight product was determined. It was shown that its formation by dimerization of the original alcohol presented an unusual path-way for the Diels-Adler reaction with elimination of one molecule of formaldehyde from two molecules of alcohol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2050–2052, September, 1989.The authors express their gratitute to A. F. Bochkov and A. B. Gagarinov for helpful discussions on the results of this work, and also to A. D. Pershin for recording the proton NMR spectra.     

Rh(I)-catalyzed cyclization of 1-arylprop-2-yn-1-ol derivatives utilizing rhodium 1,4-migration

A highly useful method for the construction of cyclopentanone derivatives fused with aromatic ring based on hydrorhodation-1,4-rhodium migration sequence is achieved. Treatment of 1-aryl-prop-2-yn-1-ols, which are easily accessible via an addition of acetylides to the corresponding aryl aldehydes, with a catalytic amount of [Rh(cod)2]2(BF4) and P(p-tolyl)3 in the presence of a base gives cyclopentanone derivatives in moderate to good yield.     

GaCl3-catalyzed allenyne cycloisomerizations to allenenes

Cycloisomerizations of allenynes to allenenes have been studied in the presence of catalytic amounts of [Au(PPh3)]SbF6 in dichloromethane or GaCl3 in toluene. Both catalytic systems are quite effective for terminal 1,6-allenynes. However, they showed different reactivities toward allenynes with di-substituents at the allenic terminal carbon. For the GaCl3-catalyzed reactions, allenenes were obtained in reasonable to high yields. However, for a Au(I)-catalyzed reaction, a triene was obtained in a poor yield. Thus, GaCl3 serves as an effective catalyst for the cycloisomerization of allenynes bearing a terminal alkyne to give cyclic allenenes in reasonable to high yields.     

PdCl2-catalyzed oxidative cycloisomerization of 3-cyclopropylideneprop-2-en-1-ones

A novel PdCl(2)-catalyzed oxidative cycloisomerization of 3-cyclopropylideneprop-2-en-1-ones, providing a facile synthesis of highly strained functionalized 2-alkylidenecyclobutanones via furan-fused cyclobutene intermediates, is reported. An interesting route to 2(3H)-furanones with a spiro-cyclopropane unit from the obtained 2-alkylidenecyclobutanones via a ring-contraction rearrangement reaction is also realized.     

PtCl2-catalyzed rearrangement of methylenecyclopropanes

Alkylidenecyclopropanes readily convert into cyclobutene derivatives on treatment with catalytic amounts of PtCl2. The reaction is strongly accelerated when performed under an atmosphere of CO (1 atm). The resulting cyclobutenes are isolated in good to excellent yields for substrates bearing aliphatic as well as aromatic substituents R on their olefinic site. If the substituent R, however, is a very electron-rich arene, the cyclobutenes initially formed react further to give dimeric products with a previously unknown 1,2,2a,7a-tetrahydrospiro[cyclobuta[a]indene-7,1'-cyclobutane skeleton. A mechanism accounting for these experimental observations as well as for a deuterium-labeling experiment is proposed which implies reactive intermediates at the nonclassical cation/carbene interface. Furthermore it is shown that the PtCl2-catalyzed cyclobutene formation can be geared with subsequent ring-opening/ring-closing metathesis (ROM/RCM) events. Finally, a convenient "one pot" method for the preparation of the alkylidenecyclopropane substrates used in this study is presented, which is based on a modified Julia-Kocienski olefination of aldehydes with readily available 1-tert-butyl-1H-tetrazol-5-yl-cyclopropyl sulfone under Barbier conditions.     

Distinct chemoselectivities in the platinum-catalyzed 1,2-carboalkoxylations of 5-alkoxypent-1-yn-3-ol derivatives

Two distinct Pt-catalyzed carboalkoxylations of alkynes are reported. The cycloisomerization of 5-alkoxypent-1-yn-3-ol derivatives 5 produces 2,6-dioxabicyclo[3.1.0]hexanes 6; the mechanism is postulated to involve a hydroxyl-triggered [3.3]-sigmatropic allyl rearrangement. As the same catalysis is extensible to their tertiary alcohol analogues 7, distinct dihydrofuranyl alcohols 8 were obtained through a [3.3]-allyl rearrangement that is not assisted by the hydroxyl group.     

Regioselective Alkylation of 5-Substituted Tetrazoles with 3-Chlorobut-2-en-1-ol in Acid Medium

Russian Journal of Organic Chemistry - The alkylation of 5-R-tetrazoles (R = H, Me, Ph) with 3-chlorobut-2-en-1-ol was studied in 1,2-dichloroethane, chlorofom, and methylene chloride in the...     

Catalytic annulation of 1-substituted-3-en-1-yn-5-als with cycloalkanones using acid-base dual catalysts

CpRu(PPh₃)₂Cl and DBU dual catalysts in combination enable a one-pot annulation of 1-R-3-en-1-yn-5-als (R = aryl, alkenyl, alkyl) and cycloalkanones to give highly substituted benzene products. This catalytic reaction consists of a tandem aldol condensation, dehydration and aromatization through a 1,7-hydrogen shift; the resulting 1-indanones and α-tetralones are obtained in moderate to good yields.     

Quantum-chemical study of the reaction of pent-4-en-2-yn-1-ol with copper,zinc, and nickel sulfides

Complexes of metal sulfides MS (M = Cu, Zn, Ni) with pent-4-en-2-yn-1-ol modeling dimethyl-(isopropenylethynyl)carbinol, a potent floating agent for benefication of nonferrous metal ores, were calculated by the B3LYP density functional theory method with the 6–31G** basis set. The adsorption mechanisms of vinylacetylenic and aliphatic alcohols were shown to vary depending on the nature of the metal sulfide. This fact can be taken into account on the flotation of mixed ores for selective metal extraction.     

KO(t)Bu-promoted three-component coupling of aldehydes and alkynes: highly efficient synthesis of 1-en-4-yn-3-ols and 2-en-4-yn-1-ols

A KO(t)Bu-promoted three-component coupling reaction of aldehydes and alkynes without a transition-metal catalyst was developed in which the sequential addition/isomerization/addition processes take place in one pot. This reaction could be developed into a straightforward and effective method for rapid access to stereodefined (E)-1-en-4-yn-3-ol and (Z)-2-en-4-yn-1-ol compounds.     

Nucleophilic sulfanylation of 1,5-disubstituted pent-2-en-4-yn-1-ones

Regioselectivity of nucleophilic addition of benzenethiols and phenylmethanethiol to 1,5-diarylpent-2-en-4-yn-1-ones in ethanol in the presence of triethylamine at 0–30°C is determined by the nucleophile nature. Phenylmethanethiol adds to the double bond, whereas benzenethiols add to the triple bond. The addition products, 1,5-diaryl-3-benzylsulfanylpent-4-yn-1-ones and 1,5-diaryl-5-(4-arylsulfanyl)penta-2,4-dien-1-ones, respectively, were isolated in 43–89% yield. Substituents in the aryl rings of the substrates did not affect the reaction direction.     

Some features of RuCl3-catalyzed periodate oxidation of 3-N-substituted 5-allenyl-2,5-dichloro-4,4-dimethoxycyclopent-2-en-1-ones

3-N-Substituted 5-(1Z-carboxymethylene)-2-chloro-4,4-dimethoxycyclopent-2-en-1-ones have been prepared from the corresponding 3-N-substituted 5-allenyl-2,5-dichloro-4,4-dimethoxycyclopent-2-en-1-ones using selective oxidative cleavage of their allene bond by the RuCl₃−NaIO₄ system. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1646–1648, September, 1997.