Acetylene derivatives propyn

Alkynes are potentially useful as building blocks in the synthesis of numerous organic compounds, and the use of disubstituted alkynes permits the formation of ortho-disubstituted derivatives. However, the commercial development of alkyne chemistry has been hampered by the high cost of most acetylenes. Indeed, only acetylene and propyne can be regarded as low-cost chemicals. Perhaps recent progress in the synthesis of alkynes (206-209) will lead to further large-scale developments. 

Lewis-acid-promoted alkylations of silylenol ethers and silyl ketene acetals [195] with Co-complexed acetylenic acetals [196] and acetylenic aldehydes [197,198] (Scheme 4-56) also proceed with fair to excellent syn diastereoselectivity, in contrast to the low selectivity reactions of the free acetylenic derivatives [199, 200]. Reactions of the complexed aldehydes with lithium enolates are stereospecific, with (Z)-enolates giving syn selectivity and ( )-enolates anti selectivity [201]. The complementary stereoselectivity of the crossed aldol reactions of free and cobalt-complexed propynals with silyl ketene 0,S-acetals has been elaborated by Hanoaka exclusive syn selectivity is exhibited by the complexes and high anti selectivity is found with pro-... 

Heats of Transfer between Solvents. Kurkchi and logan (147) have used gas-liquid chromatography to determine specific retention volumes of acetylene (23), propyne (24), and 1-butyne (25) in eight solvents (isooctane, 9,18,25,26,28,41,52) at a number of temperatures, and thence have derived heats of solution, AHy, and of transfer between solvents, AHij. The later quantities (transfer from isooctane to HBA solvents) are well correlated by /8 and x ... 

Thiazoles. A mixture of 3-chloro-l,3-diphenyl-l-propyne, thiourea, and ethanol heated 1.5 hrs. 2-amino-4-benzyl-5-phenylthiazole. Y 87%. F. e., also imidazoles from guanidine, from a,/ -acetylenehalides s. Y. Yura, Chem. Pharm. Bull. 10, 376, 372 (1962) from other acetylene derivatives s. Chem. Pharm. Bull. 10, 1087, 1094. 

The reactivity of OsHCl(CO)(P Pr3)2 toward alkynes depends on the type of alkyne used. Whereas phenylacetylene, propyne, and acetylene react by insertion to give the five-coordinate alkenyl derivatives Os ( >CI I=CHR Cl(CO)(PIPr3)2 (R = Ph, Me, H),31,33 the reaction with methylpropiolate affords a mixture of Os C(=CH2)C(OMe)0 Cl(CO)(P,Pr3)2 and 0s ( )-CH=CHC02Me Cl(C0) (P Pr3)234 (Scheme 3), and tert-butyl acetylene and diphenylacetylene are inert. 

A more complex carbonylation process is involved in the formation of bisbutenolides (bifurandiones) from cobalt carbonyl-catalyzed carbonylation of alkynes112 117 (Scheme 68). The trans derivative (53) is formed in good yield from acetylene,112 but yields from substituted acetylenes (e.g., propyne)... 

The presence of the endothermic triply-bonded acetylene (ethyne) group confers explosive instability on a wide range of acetylenic compounds (notably when halogen is also present) and derivatives of metals (and especially of heavy metals) [1], Explosive properties of butadiyne, buten-3-yne, hexatriyne, propyne and propadiene have been reviewed, with 74 references [2], The tendency of higher acetylenes to explosive decomposition may be reduced by dilution with methanol [3], The class includes the separately treated groups ... 

Similar metalation studies were carried out on l,3-bis(trimethylsilyl)propyne. The IR bands observed in the 2200-1600 cm region of acetylenes, allenes and aU the Uthiated derivatives are summarized in Table 8. 

The authors noticed that polylithiated phenylallenes have a vibrational behaviour similar to that of polylithiated propynes and butynes (Table 8) . The monolithium compounds from terminal acetylenes were found to have acetylenic structures (2050 cm ), whereas the monolithium derivatives of non-terminal acetylenes could exist in either acetylenic (2000 cm ) or allenic (1870-1850 cm ) forms (Table 8) °. The polylithium... 

Bowman et al. reported the total synthesis of ellipticine (228) involving an imidoyl radical cascade reaction (730). For this key step, the required imidoyl radical was generated from the imidoyl selanide 1290, which was obtained from ethyl 2-(4-pyridyl)acetate (1286). Reaction of 1286 with LDA, followed by addition of methyl iodide, led to the corresponding methyl derivative 1287. Treatment of 1287 with 2-iodoaniline (743) in the presence of trimethylaluminum (AlMes) afforded the amide 1288. Using Sonogashira conditions, propyne is coupled with the amide 1288 to afford the aryl acetylene 1289. The aryl acetylene 1289 was transformed to the... 

Acetylenic compounds may in some cases be suitable sources of 1,3-dioxo precursors as shown for propynal in the synthesis of 85a-d.62,l27 131 Similarly, the preparation of probable 4//-pyran derivative 91 (61.7%) may be explained by a hydration catalyzed with Zn2+ ions, which leads to a 1,5-dicarbonyl intermediate.138... 

The triple bond of the nitrile group can be cotrimerized with two alkynes to produce pyridines. The cobalt-catalysed cocyclization of alkyne and nitrile in a ratio of 2 1 is a good synthetic route to pyridine derivatives [70], Two regioisomers, 174 and 175, are obtained by the reaction of propyne with MeCN. The reaction is carried out in a large excess of MeCN, and potentially useful for commerical production of pyridine derivatives [71]. The reaction of acetylene itself with various nitriles produces the a-substituted pyridine 176 in the presence of water under irradiation [72], HCN cannot be used for this cocyclization. The reaction has been applied to alkaloid synthesis. 

Acetylenes and cyclopropenes (37) are related to each other in the same formal way as olefins and cyclopropanes are. Recall that cyclopropanation of ethylene is almost slightly endothermic and the endothermicity was asserted to increase by some (3 2) kJ moT per alkyl group. Cyclopropanation of acetylene to form cyclopropene (37, X = X = H) is endothermic by (48.9 2.6) kJ mol. Cyclopropanation of propyne (monomethy-lacetylene) to form 1-methylcyclopropene (37, X = Me, X = H) has an increased endothermicity of (58.7 1.4) kJ mol. By contrast, the cyclopropanation of 2-butyne (dimethy-lacetylene) using a derived value for the enthalpy of formation of 1,2-dimethylcyclopropene (37, X = X = Me) has an accompanying endothermicity of only 41 kJ moT. We suspect that the last value is in error and so suggest remeasurement of the enthalpy of formation of dimethylcyclopropene as well as measuring the enthalpy of formation of other cyclo-propenes. ... 

P-Acetylenic alcohols (11, 378). The propargyltitanium reagent derived from 1-trimethylsilyl-3-(tetrahydropyranyloxy)propyne (1) reacts with crotonaldehydes to afford the P-acetylenic alcohol 2 with high stereoselectivity. This alcohol was used in a stcr-eocontrolled synthesis of the natural antibiotic ( )-asperlin (6). 

SAFETY PROFILE The carbon-carbon triple bond is explosively unstable in many acetylenic compounds. Both the lower alkynes (i.e., propyne, butadyne, etc.) and higher compounds may undergo explosive decomposition. The presence of halogens and heavy metal derivatives may increase these explosive tendencies. See also ACETYLENE, ACETYLIDES, and specific compounds. 

Several disubstituted acetylenes containing other heteroatoms have been found to polymerize Derivatives of propiolic acid (PhC = CC02H, H02CC=CC02H) can be polymerized by MoCls— cocatalyst40). The polymerization of l-(ferrocenyl-l-propyne) is effected by WCl —Ph Sn 49). The MW s of these polymers, however, are not very high. 

A further development of the Reppe acrylic acid synthesis is the reaction, described in recent literature, of the noble metal-catalyzed carbonylation of higher acetylenes to give the corresponding acrylic acid derivatives. Thus, for example, the Pd-catalyzed carbonylation of propyne (eq. (10)) in the presence of methanol leads directly to methyl methacrylate [23]. Based on this work. Shell has developed a new production process for methyl methacrylate [24]. The propyne required can be isolated from the product streams from crackers, (cf. Section 2.3.2.3). 

RC CNa and derived products. Tetrolic acid is prepared by conversion of propyne into the sodio derivative, carbonation, and acidification. For the preparation of 1-hexyne, Campbell and Campbell passed acetylene into 3 1. of liquid... 

Perlithiopropyne 26 (CjLiJ shows a strong absorption at 1675 but no band in the C=C stretching region between 2130 and 2190 cm The same is true for perlithiopentadiyne 157 (CjLiJ >, and it was therefore believed that the polylithium derivatives of propyne and pentadiyne all have allenic structures in solution, i.e. 26b and 157b instead of acetylenic 26a and 157a. 

Pyrazole derivatives can be prepared analogously from alkynes e.g., reaction of propynal with ethereal diazomethane gives 84% of pyrazole-3-carbaldehyde and that with diazoacetic ester gives 86% of ethyl 5-formyl-pyrazole-3-carb-oxylate.18 Further, pyrazole itself is readily accessible from acetylene and diazomethane.19... 

Acetylenes. Propyne can be converted into the 1,3-dilithio derivative by reaction with 2 eq. of -butyllithium in the presence of 1 eq. of TMEDA or DABCO (-60°, hexane-ether). This derivative reacts with electrophiles initially at the propargylic carbon, then at the terminal acetylide site. The reactions can be carried out in sequence in one pot. ... 

The anti-proliferative effects of some dicobalt hexacarbonyl alkyne complexes derived from aspirin 21, from diphenyl acetylene 22, and from 2-propyn-l-ol have been studied on various cell lines, including... 

For the polymerization of disubstituted acetylenes, M0CI5 and WCl6 alone are inactive, and it is necessary to use the catalyst/cocatalyst mixtures (16), which are active for sterically less crowded monomers (e.g., 2-octyne and 1-chloro-l-octyne). In contrast, NbCls and TaCls by themselves polymerize disubstituted acetylenes with bulky substituents such as 1-(trimethylsilyl)-l-propyne. Diphenylacetylene and its derivatives, however, are polymerizable only with the TaCls-cocatalyst systems. The Nb and Ta catalysts selectively afford cyclotrimers from most monosubstituted acetylenes. 

---