Diyne, hydration

Almost simultaneously, Sehroth reported that diaeetylene reaets with a hydrazine hydrate solution at 80°C for 4 h to form methylpyrazoles (13) in 80% yield (69ZC108 69ZC110). In the same year, other data eoneeming the reaetion of hydrazine with diaeetylene (65°C, EtOH, yield 65%), hexa-2,4-diyne, and 1,4-diphenylbuta-1,3-diyne were reported (69JOC999). Later, BASF (93GEP4137011) proposed to earry out the proeess at 100°C in a polar solvent with a diaeetylene eoneentration of 14-18% in an inert gas. The yield of methypyrazoles was 90% (post-reetifieation purity 99%). 

In the reaetion of methyldiaeetylene with hydrazine hydrate, both 3-ethylpyrazole (14) and 3,5-dimethylpyrazole (15) were formed in a 4 1 ratio (73DIS). Both pyrazoles were preparatively isolated (3,5-dimethylpyrazole is erystalline and ethylpyrazole is a liquid) and identified by eomparison with authentie samples. These data show that primary attaek of monosubstituted 1,3-diynes by hydrazine is mainly direeted toward the terminal aeetylenie bond. 

The hydration of conjugated diynes readily affords 1,3-diketones. The hydration may be acid- or mercuric sulfate-catalyzed. The Rupe rearrangement is observed under general acid catalysis (equation 204).310... 

Hydroboration followed by oxidation provides an indirect route for hydration of diynes and constitutes an efficient route to acetylenic ketones as demonstrated by the synthesis of 206 in 75% yield from diyne 205... 

Anhydrous material, prepared by refluxing the hydrate with acetic anhydride and washing the insoluble product with dry ether, is used in methanol-pyridine for the oxidative coupling of terminal acetylenes to diynes. Mechanism. Review. ... 

Addition Reactions - The allyl ketone (9) is the product formed on photohydration of the diyne (10). The photohydration step arises from the triplet excited state of (10). The polarization within the excited state is the key to the outcome of the reaction and is such that the protonation occurs at Cl. Shim has published a short review dealing with the hydration of such systems. 

The ability of water to attack the ruthenium-carbon double bond suggested that the ruthenacyclopentadiene might add water as depicted in Scheme 1.4. Remarkably, heating a tethered diyne in aqueous acetone to 60 °C in the presence of the trisacetonitrile complex 16 gave a nearly quantitative yield of the hydrated cyclization product as depicted in Equation 1.29 [26], Unsymmetrical diynes showed exquisite regioselectivity wherein the water attacked the least sterically hindered alkyne carbon (Equation 1.30). 

Only rarely is proton loss observed from the intermediate cation derived from acylation of a terminal alkyne. In contrast, acylation of alkynylsilanes provides an excellent strategy for the synthesis of alkynyl ketones. " Here, it is apparent that elimination of the silyl substituent competes very effectively with capture of a nucleophile. Acylation of bis(trimethylsilyl)ethyne" provides a convenient route to terminal alkynic ketones, particularly since desilylation can be carried out using bases as weak as dilute aqueous borax, conditions mild enough to prevent the ready hydration of the triple bond (Scheme 25)." Silylated diynes are also excellent substrates for Friedel-Crafts acylation. ... 

The reactivity of butadiene and -diyne derivatives in layer perovskites demonstrates the suitability of these complex salts to act as templates for solid state reactions. Besides the polyaddition also other chemical reactions should be able to occur with a high stereoselectivity, as for example isomerizations, or addition reactions, such as hydrations, halogenations, oxidations, or polycondensations. In any case it will... 

Simple thermal substitution of CO in the reaetion of Ru3(CO)i2 with hexa-2,4-diyne-l,6-diol leads to Ru3(CO)9(jU-CO) (HO)CH2C=CC=CCH2(OH) with a parallel alkyne. The acetylide complexes (/i-H)Ru3(GO)9 C=CCR(OH)R (R = Me, R = Me, Ph) and their dppm (dppm = bis(diphenylphosphino)-methane) derivatives are also obtained (in four optical isomers) via thermal substitution H and C NMR fluxion-ality and hydration-dehydration reactions have been studied. Dehydration leads to the vinylacetylene derivatives (/i-H)Ru3(CO)7(dppm)(C CC=CH2Ph), formed by loss of the OH group and of one hydrogen of the methyl substituent on the same carbon atom. ... 

Diaryl fiirans are synthesized by double addition of O—H bonds to 1,4-diaryl-1,3-diynes [15]. The hydration reaction is catalyzed by a Cu(I)-phenanthroline catalyst in dimethyl sulfoxide (DMSO) at 70 °C ... 

Table 20.3, entries 1 to 6) [11]. The gold(I)-NHC complex also catalyzed hydration of various 1,3-diynes in mixed l,4-dioxane-H20 solvent (entries 7 to 10) [12],... 

A facile electrocyclization cascade has been reported to occur when diynes (46) are halogenated with NBS or NIS in the presence of a catalytic amount of AgBp4 (Scheme 3). The initial attack by X+ apparently generates the vinylic cation (47) that undergoes cyclization via (48) to produce the benzylic alcohol (49). The silver(I) catalyst then promotes aromatization with a concomitant hydration, giving rise to the halo-substituted benzo[a]fluorenols (50). ... 

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