Residues alkyne

Two types of substituents linked to the steroid rings arc involved in the Mannich reaction, namely, methyl ketone and alkyne residues. The former react on the methyl group, and the latter react chemo.selectivcly on the alkyne hydrogen atom when copper salts are employed as a catalyst. ... 

Bibenzocyclooctyne and bicyclo [6.1.0] non-4-yne-modified 2 -deoxyuridine triphosphates can be further employed for PCR reactions, with standard DNA polymerases allowing internal labeling of DNA with multiple strained alkyne residues [10]. Fluorescent labeling was demonstrated with azide-modified fluo-rophores [10]. 

The simple cyclopropylmethoxycarbenechromium complex 142 reacts with alkynes to afford cyclopentenones 143 and 144 via the cyclopentadiene intermediate 145, which is hydrogenated with the aid of the chromium(O) residue and water (Scheme 31) [100-103]. Formation of 145 can be regarded as... 

Besides short ELPS, longer ELPs have also been conjugated to synthetic polymers. In one approach, Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry was applied. For this purpose, ELPs were functionalized with azides or alkynes via incorporation of azidohomoalanine and homopropargyl glycine, respectively, using residue-specific replacement of methionine in ELP via bacterial expression [133]. More recently, an alternative way to site-selectively introduce azides into ELPs was developed. Here, an aqueous diazotransfer reaction was performed directly onto ELP[V5L2G3-90] using imidazole-1-sulfonyl azide [134]. 

The synthesized CPMV-alkyne 42 was subjected to the CuAAC reaction with 38. Due to the strong fluorescence of the cycloaddition product 43 as low as 0.5 nM, it could be detected without the interference of starting materials. TMV was initially subjected to an electrophilic substitution reaction at the ortho-position of the phenol ring of tyrosine-139 residues with diazonium salts to insert the alkyne functionality, giving derivative 44 [100]. The sequential CuAAC reaction was achieved with greatest efficiency yielding compound 45, and it was found that the TMV remained intact and stable throughout the reaction. 

The 3-oxo-2-pyrazolidinium ylides 315, easily available by reaction of the corresponding pyrazolidin-3-one with aromatic aldehydes, function as 1,3-dipoles in cycloaddition reactions with suitable alkenes and alkynes to provide the corresponding products. When unsymmetrical alkynes are used, mixtures of both possible products 316 and 317 are usually obtained (Equation 45). The regioselectivity of cycloadditions of the reaction with methyl propiolate is influenced by the substituents on the aryl residue using several 2,6-di- and 2,4,6-trisubstituted phenyl derivatives only compound 316 is formed <2001HCA146>. Analogous reactions of 3-thioxo-l,2-pyrazolidinium ylides have also been described <1994H(38)2171>. 

The palladium-catalyzed C-Se bond formation79-81 and the platinum-catalyzed carboselenation of alkynes with selenoesters have been reported in analogy with the thiolate chemistry. An electron-withdrawing or electron-donating group on the aromatic residue leads to the formation of the desired carboselenation product with acceptable yields. Functionalities like benzyl, hydroxyl, or nitrile group are tolerant with the reaction conditions. This method provides a new access to the functionalized vinylselenide 60,82 molecules of interest as key intermediate (Scheme 19) 85... 

Method B TBA-Br, (0.96 g, 2 mmol) is added to the alkyne (2 mmol) in MeOH (100 ml) and the mixture is stirred until the reaction is complete, as shown by TLC analysis. The solvent is removed under reduced pressure and the residue is taken up in Et20 (50 ml). The ethereal solution is washed well with aqueous Na2S203 (5%) and H20, dried (MgS04), and evaporated. The dibromoalkenes and dibromodimethoxyalkanes are separated by chromatography (Table 2.14). 

Anti-tellurosulphonation of 1-alkynes.A solution of alkyne (1.1 mmol), sodium arylsul-phinate (5 mmol) and diorgano ditelluride (0.5 mmol) in 5 mL of 80% aqueous acetic acid was heated at 80°C for 24 h (R=Ph, 5.2 h). The reaction mixture was diluted with 20 mL of AcOEt, washed with saturated aqueous sodium bicarbonate, dried over Na2S04 and concentrated in vacuum. Crude products, were concentrated under vacuum, and the residues were purified by preparative TLC on silica gel (AcOEt/hexanes, 1 10), treated with 1 equiv of Br2 in AcOEt and concentrated under vacuum. The residues were purified by recrystallization with CH3OH/HCCI3. 

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