Synthesis of (1E)-1-Chloroalk-1-en-4-ynes

Russian Journal of General Chemistry - A stereoselective method has been developed for the synthesis of (1E)-chloroalk-1-en-4-ynes, promising precursors to 1,4-enynes, on the basis of alkynylation...     

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.     

Novel capto-dative (Z,E)-2-(alkylthio)alk-2-en-4-ynals: synthesis and heterocyclization

An efficient synthesis of new (Z,E)-2-(alkylthio)alk-2-en-4-ynals by aldol condensation reaction of ynals with (alkylthio)-acetaldehydes using NaOH/DMF system has been developed.The reaction of these products with N,N-diphenylethylene-diamine and p-tosylmethyl isocyanide proceeds at the carbonyl group to form the corresponding imidazolidine and oxazole derivatives.     

Stereoselective Synthesis of Difunctionalized 1,3-Dienes Containing Silicon and Selenium via Hydrozirconation of (Z)-3-(Trimethylsilyl)alk-3-en-1-ynes

Sonogashira coupling of (E)-α-iodovinylsilanes 1 with (trimethylsilyl)-acetylene gave (Z)-1,3-bis(trimethylsilyl)alk-3-en-1-ynes 2, which underwent a desilylation reaction to afford (Z)-3-(trimethylsilyl)alk-3-en-1-ynes 3 in good yields. (1E,3Z)-1-Arylseleno-3-(trimethylsilyl)-substituted 1,3-dienes 5 could be synthesized stereoselectively via hydrozirconation of (Z)-3-(trimethylsilyl)alk-3-en-1-ynes 3, followed by trapping with arylselenenyl bromides.     

Synthesis and Fungicidal Activity of Substituted (E)-3-Phenyl-1-(pyridin-3-yl)prop-2-en-1-one (E,Z)-O-Alkyl- and O-Benzyloximes

Russian Journal of Organic Chemistry - Previously unknown substituted (E)-3-phenyl-1-(pyridin-3-yl)prop-2-en-1-one (E,Z)-O-alkyl- and O-benzyloximes were synthesized by oximation of...     

Deamination of 3-(dialkylamino)-1,4-diarylhex-5-en-1-ynes during vacuum distillation

During vacuum distillation of 3-(dialkylamino) derivatives of 1,4-diphenyl- and 4-phenyl-1-(p-chlorophenyl) hex-5-en-1-ynes deamination occurs resulting in a high yield of p-diarylbenzenes. The amines transformation into terbenzenes is a domino-reaction: first step consists in the β-elimination of secondary amines with the generation of conjugated dienyne which via an electrocyclic reaction transforms into cyclic allene intermediate. The latter after 1,3- or 1,5-hydride shift quickly converts into the final reaction products.     

Asymmetric total syntheses of (-)-antofine and (-)-cryptopleurine using (R)-(E)-4-(tributylstannyl)but-3-en-2-ol

The asymmetric total syntheses of the representative phenanthroindolizidine and phenanthroquinolizidine alkaloids, (-)-antofine and (-)-cryptopleurine, are described. An efficient synthetic pathway to the key intermediate 12, in enantiomerically pure form, was achieved by using a chiral building block (R)-9 and the Overman rearrangement with a total transfer of chirality. The problem of constructing the pyrrolidine and piperidine rings was successfully addressed, primarily by using a ring-closing metathesis reaction and a cross-metathesis reaction, respectively.     

Gas-phase rate coefficients for the reactions of nitrate radicals with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene at room temperature

Rate coefficients for reactions of nitrate radicals (NO3) with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene were determined to be (6.55 +/- 0.78)x 10(-13) cm3 molecule(-1) s(-1), (3.78 +/- 0.45)x 10(-13) cm3 molecule(-1) s(-1), (5.30 +/- 0.73)x 10(-13) cm(3) molecule(-1) s(-1), (3.83 +/- 0.47)x 10(-13) cm(3) molecule(-1) s(-1), (4.37 +/- 0.49)x 10(-13) cm(3) molecule(-1) s(-1), (3.61 +/- 0.40)x 10(-13) cm3 molecule(-1) s(-1) and (8.9 +/- 1.5)x 10(-12) cm3 molecule(-1) s(-1), respectively. We performed kinetic experiments at room temperature and atmospheric pressure using a relative-rate technique with GC-FID analysis. The experimental results demonstrate a surprisingly large cis-trans(Z-E) effect, particularly in the case of the pent-2-enes, where the ratio of rate coefficients is ca. 1.7. Rate coefficients are discussed in terms of electronic and steric influences, and our results give some insight into the effects of chain length and position of the double bond on the reaction of NO3 with unsaturated hydrocarbons. Atmospheric lifetimes were calculated with respect to important oxidants in the troposphere for the alkenes studied, and NO3-initiated oxidation is found to be the dominant degradation route for (Z)-pent-2-ene, (Z)-hex-3-ene and (E)-3-methylpent-2-ene.     

Straightforward Preparation of (2E,4Z)-2,4-Heptadien-1-ol and (2E,4Z)-2,4-Heptadienal

Abstract

A concise synthesis of (2E,4Z)-2,4-heptadien-1-ol and (2E,4Z)-2,4-heptadienal is presented. Commercially available (Z)-2-penten-1-ol was converted to ethyl-(2E,4Z)-2,4-heptadienoate by reaction with activated MnO₂ and (carboethoxymethylene)triphenylphosphorane in the presence of benzoic acid as a catalyst. Ethyl-(2E,4Z)-2,4-heptadienoate was converted to (2E,4Z)-2,4-heptadien-1-ol with LiAlH₄. The alcohol was partially oxidized to (2E,4Z)-2,4-heptadienal with MnO₂. The title compounds are male-specific, antennally active volatile compounds from the Saltcedar leaf beetle, Diorhabda elongata Brulle (Coleoptera: Chrysomelidae) and have potential use in the biological control of the invasive weed saltcedar (Tamarix spp).     

Highly selective synthesis of (E)-3-methyl-1-trialkylsilyl-3-en-1-ynes via trans-selective alkynylation catalyzed by Cl2Pd(DPEphos) and stereospecific methylation with methylzincs catalyzed by Pd(tBu3P)2

[reaction: see text] trans-Selective (>or=98%) monoalkynylation of 1,1-dibromo-1-alkenes and 1,1-dichloro-1-alkenes catalyzed by Cl(2)Pd(DPEphos) followed by stereospecific methylation with Me(2)Zn or MeZnX (X= Cl or Br) catalyzed by Pd((t)()Bu(3)P)(2) provides an efficient and stereoselective (>or=98%) route to 5, convertible to a wide variety of enynes and conjugated dienes. In the cases of 1,1-dibromo-1-alkenes, the Sonogashira alkynylation may also be satisfactory, but it is distinctly less satisfactory than the alkynylzinc reaction in cases where 1,1-dichloro-1-alkenes are used.     

(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes as (E)-1-(1,3-butadienyl) synthons

(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes (E/Z=9), prepared from 4-trimethylsilyl-1-buten-3-ol, $\text{n}$-butyllithium and benzenesulfenyl chloride and oxidation of the intermediate (E)- and (Z)-1-benzenesulfinyl-4-trimethylsilyl-2-butenes with hydrogen peroxide, react with $\text{n}$-butyllithium and then primary halides to give 4-benzenesulfonyl-1-trimethylsilyl-2-alkenes which are rapidly 1,4-debenzenesulfonyltrimethylsilated to (E)-1,3-alkadienes by tetra-$\text{n}$-butylammonium fluoride at O°C.     

Palladium catalysed regio- and stereoselective synthesis of (E)-4-aryl-1,3-bis(trimethylsilyl)but-3-en-1-ynes

A practical and general synthetic approach to a series of 4-aryl-but-3-en-1-ynes is described. In the presence of palladium complexes a variety of aryl bromides (or iodides) undergo coupling with two equivalents of trimethylsilylacetylene with the formation of (E)-4-aryl-1,3-bis(trimethylsilyl)but-3-en-1-ynes. The protocol is simple, efficient, and affords synthesis of regio- and stereoselectively target products in good to high yields.     

Synthesis,Crystal Structure and Anti-ischemic Activity of(E)-1-(4-(Bis(4-methoxyphenyl)methyl)piperazin-1-yl)-3-(4-acetoxy-3-methoxyphenyl)prop-2-en-1-one

A new cinnamide derivative,(E)-1-(4-(bis(4-methoxyphenyl)methyl)piperazin-1-yl)-3-(4-acetoxy-3-methoxyphenyl)prop-2-en-1-one(C31H34N2O6,Mr = 530.60),has been synthesized by the condensation of 1-(bis(4-methoxyphenyl)methyl)piperazine and(E)-3-(4-acetoxy-3-methoxyphenyl)acrylic acid.The compound was characterized by 1H NMR,13 C NMR,H RMS and single-crystal X-ray diffraction.The crystal belongs to the orthorhombic system,space group P212121 with a = 24.946(5),b = 7.6380(15),c = 14.555(3) ?,V = 2773.3(10) ?3,Z = 4,Dc = 1.271 g/cm3,F(000) = 1128,μ = 0.088 mm-1,Mo Kα radiation(λ = 0.71073 ?),the final R = 0.0641 and w R = 0.1170.A total of 3009 unique reflections were collected,of which 1760 with I 2σ(I) were observed.Intramolecular C(17)–H(17B)···O(3) and C(22)–H(22A)···O(3) interactions as well as intermolecular C(27)–H(27A)···O(3) hydrogen bonds help to stabilize the crystal structure.The title compound was evaluated for the anti-ischemic activity in vitro and in vivo.The bioassay results indicated that the title compound displayed efficient activities against glutamine-induced neurotoxicity in PC12 cells and significantly prolonged the survival time of mice subjected to acute cerebral ischemia.     

Cross coupling reactions of organozinc iodides with solid-supported electrophiles: synthesis of 4-substituted benzoic and 3-substituted (E)- and (Z)-propenoic acids and amides

The solid-supported iodobenzoic acid derivatives 8-10 were coupled with a range of organozinc reagents 1-4 under palladium(o) catalysis. The coupled products released by acidic cleavage with TFA were obtained in high purities after recrystallisation. Analogous coupling of solid-supported (E)- and (Z)-3-iodoacrylic acids 18a, 18b, 19 and 20 gave (E)- and (Z)-alpha,beta-unsaturated acids and amides 21-27 stereospecifically.     

1,5-Electrocyclization of 1-alkyl- 3-[(2Z)-2,4-diaryl-4-oxobut-2-en-1-yl]-1H-benzimidazol-3-ium bromides

Cyclization of 1-alkyl-3-[(2Z)-2,4-diaryl-4-oxobut-2-en-1-yl]-1H-benzimidazol-3-ium bromides occurs in the presence of MeONa at a reduced temperature of 5–10°C via a 1,5-electrocyclization mechanism to give 3a,4-dihydro-3H-pyrrolo[1,2-a]benzimidazoles. These are unstable under the reaction conditions and are readily converted to {1-[2-(alkylamino)phenyl]-4-phenyl-1H-pyrrol-3-yl}(phenyl)methanones.