Alkynes compounds

Hydrazoyl halides are useful reagents for the synthesis of pyrazolines and pyrazoles (80JHC833). The elimination of HX, usually with triethylamine, is now the preferred method for the generation of the nitrilimine (621) in situ. Although in some cases it is not clear if the mechanism involves a nitrilimine (621) (as for example in the Fusco method in which sodium salts of /3-diketones are used), in other reactions it is the most reasonable possibility. For example, the synthesis of pyrazolobenzoxazine (633) from the hydrazoyl halide (631) probably occurs via the nitrilimine (632). Trifluoromethylpyrazoles (634) have been prepared by the reaction of a hydrazoyl halide and an alkynic compound in the presence of triethylamine (82H(19)179). 

Monosubstituted hydrazones react with alkenes and alkynic compounds to yield pyrazolidines and pyrazolines, respectively (71LA(743)50, 79JOC218). Oxidation often occurs during the reaction and pyrazoles are isolated as the end product. 

Figure 35 X-ray structures of the copper alkyne compounds 85-87. 85 reproduced with permission from ACS publications. 85 and 87 reproduced with permission from Elsevier. 

Figure 17.15 The small carboxylate-alkyne compound 4-pentynoic acid can be used to modify proteins at their amine groups with EDC to provide alkyne sites for click chemistry-mediated conjugation. The subsequent reaction of an azido-PEG-modified gold nanoparticle with the alkynyl-protein in the presence of Cu1+ yields the triazole-coupled protein.

Anodic oxidations of the Mo(II) bis-cyclopentadienyl alkyne compound Mo(jj -C5H5)2( i -C2Ph2), and of metal-alkene analogs such as Mo(j -C5H5)2(j7 -C2H4) involve a reversible one-electron oxidation at very facile potentials. The v(CC) alkyne stretch in the IR spectrum of 17-electron Mo-alkyne cation (1824 cm ) was shifted by 50cm to a higher wave number to that of its parent, consistent with a decrease in the metal-alkyne interaction in the Mo(III) cation. 

The reaction of pyridines with alkynic compounds provides a useful synthesis of indolizines containing ester groups in the five-membered ring (78AHC(23)263). 

A one-step synthesis of furo[3,2-c]- and furo[3,2-6]-pyridines has been realized using a cycloaddition reaction of an alkynic compound with 3,5-dichloropyridine 1-oxide (Scheme 15) (75JA3227). Formation of (75) probably proceeds through a 1,2-dihydropyridine (73) with a subsequent 1,5-sigmatropic shift to (74) elimination of hydrogen chloride yields... 

Allyl alcohols can be produced catalytically by oxidation of alkenes with TBHP in the presence of small amounts of Se02 (equation 128). In contrast to the stoichiometric reaction, this catalytic oxidation can be performed under mild conditions (r.t., CH2C12 solvent).356 Alkynic compounds undergo a predominant allylic dihydroxylation upon reaction with TBHP/CH2C12 (equation 129) 357... 

Treatment of 7,9-dialkylxanthinium cations (410a) with n-butyllithium forms the corresponding ylide (410b) which reacts in a 1,3-dipolar addition with alkyne compounds to give 5-pyrrolouracils (411) and/or pyrrolo[l,2-/]pteridines (412) (Scheme 67) <82H(19)1845>. 

Mass spectral fragmentation patterns in the spectra of these compounds are in accord with the formation of alkynes. The first step in the fragmentation of 1,2,3-selenadiazoles is the loss of N2 followed by extrusion of selenium and formation of the corresponding alkyne. The abundance of the alkynic ion in the mass spectrum appears to be dependent on the nature of the substituent group present in the selenadiazole. When the alkynic ion cannot be stabilized by the formation of a cation on the adjacent carbon atoms, the abundance of the alkynic ion decreases (10% in the parent compound and zero for 4-f-butyl-l,2,3-selenadiazole). On the basis of the mass spectral pattern it is possible to predict the yield of the alkynic compound formed through pyrolysis or photolysis of a given... 

Cycloaddition reactions with alkynic compounds are illustrated by the reaction of methyl propiolate with (78) to form (79), and by the reaction of benzyne with (78) to form (80)... 

A ring transformation takes place in the reaction of 3-mercapto- or 3-acylthio-3-isothiazo-line-5-thiones (331) with reactive alkynic compounds in boiling acetonitrile this reaction produces the 1,3-dithiole derivatives (332) in good yields (80JCS(P1)2693, 80H(14)785). 

Similarly, reaction of 3-chloroacylthio-3-isothiazoline-5-thiones (333) with reactive alkynic compounds proceeds with formation of the 1,3-dithiole derivatives (334) which contain thiazolone or 5,6-dihydro-l,3-thiazin-4-one rings (81H(16)595). 

Both double and triple bonds are multiple bonds. Therefore alkynes are unsaturated hydrocarbons, just as alkenes are. To name alkynes and draw their structures, you follow the same rules that you used for alkenes. The only difference is the suffix -yne, which you need to use when naming alkyne compounds. Also, remember to count the number of bonds for each carbon. An alkyne bond counts as three bonds. 

Although the reactions between alkynes or alkenes and metal clusters are the main source of alkyne-substituted complexes, there are other reagents which can produce similar products. Two such reagents are tetraphenylcyclopentadienone, which in the reaction with Ru3(CO)i2 produces Ru3(CO)10(PhCCPh) (167), and dimethyl-vinylarsine, which has been made to react with several carbonyl clusters [Eq. (8)] (168, 169). In the reaction of M3(CO)12 (M = Ru, Os) with a number of tertiary phosphines and aromatic alcohols, an oxidative addition takes place and benzyne-triosmium compounds are obtained (170-176). The fact that Os3(CO)uPEt3 can be converted into an alkyne compound (177) suggests that the conversion goes through substituted intermediates. Carbene derivatives of clusters have also... 

One of the most important links between alkylidyne and alkyne compounds is that one of the first synthetic routes for cobalt al-kylidynes involved alkynes as reagents (264-268). In later studies, several other synthetic routes to cobalt (269-280), rhodium (281, 282), iron (283-285), molybdenum (286, 287), ruthenium (288-292), osmium (293, 294), nickel (295, 296), and some mixed-metal (165, 297-302) clusters have been developed. Reagents employed include carbynes (166, 277, 280), alkali metals (269), carbon disulfide (275), dithioesters (276, 282), RCC13, and acids (281, 282). 

Substituted alkynic compounds result when two cycloreversions are carried out on the same carbon-carbon bond of a bis-DA adduct. Thermolysis of bis-adduct (94) produced alkyne (95) and anthracene via two rDA cycloreversions as shown in equation (41). ... 

In Chapters 10 and 11 we turn our attention to alkenes and alkynes, compounds that contain one and two n bonds, respectively. Because n bonds are easily broken, alkenes and alkynes undergo addition, the third general type of organic reaction. These multiple bonds also make carbon atoms electron rich, so alkenes and alkynes react with a wide variety of electrophilic reagents in addition reactions. 

In Chapter 11 we continue our focus on organic molecules with electron-rich functional groups by examining alkynes, compounds that contain a carbon-carbon triple bond. Like alkenes, alkynes are nucleophiles with easily broken n bonds, and as such, they undergo addition reactions with electrophilic reagents. 

Some alkyne compounds have been isolated with platinum and nickel. The first were obtained from m-PtCl2(PR3)2 with hydrazine in the presence of the alkyne 8) or from bis(triphenylphosphine)-platinum(0) and the alkyne 184). They correspond to Pt(PR3) 2 (alkyne) and, like the corresponding nickel derivatives, can be considered tricovalent platinum (0) derivatives or square planar platinum(II) derivatives. 

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