Carbonylative 1-hexyne

The carbonylation of 2-methyl-3-butyn-2-oI (50) in benzene gives teraconic anhydride (51). Fulgide (53) (a dimethylenesuccinic anhydride derivative), which is a photochromic compound, can be prepared by the carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (52)[21], The reaction proceeds under milder conditions when PdlOAc) is used as a catalyst in the presence of iodine [23],... 

An iron-catalyzed carbonylation reaction of alkynes 120 forming succinimides 121 by the aid of Fe(CO)5 78 or [Fe3(CO)i2] 119 has been reported by Beller et al. (Scheme 31) [94]. This reaction seems interesting as iron-carbonyl complexes are kinetically relatively inert. As a model system 3-hexyne was reacted with excess ammonia under 20 bar CO pressure. Employing a higher pressure leads to... 

Burger2 has shown that alkynes undergo both Lewis acid-catalyzed and thermal carbonyl-yne reactions with 3,3,3-trifluoropyruvates to give allenes. Reaction of 1 (Equation (2)) occurs to give a 1 1 mixture of diastereomeric allenyl carbinols 2. Alternatively, reaction of hexyne 1 and methyl trifluoropyruvate with MgBr2-OEt2 at low temperature afforded 2 as an 8 1 mixture of diastereomers. The thermal reaction does not suffer from allylic alcohol byproducts arising from reaction of the substrate with the Lewis acid.3... 

In the first rhodium-catalyzed carbonylative silylcarbocyclization (CO-SiCaC), which was reported in 1992 [12, 13], silylcyclopentenone 9 was isolated as a minor product in the silylformylation of 1-hexyne 8 (Scheme 7.4). Under optimized conditions using Et3SiH and ( BuNC)4RhCo(CO)4 as the catalyst at 60°C, 9 is formed in 54% yield [13]. A possible mechanism proposed for this intermolecular CO-SiCaC is shown in Scheme 7.4 [13]. In this mechanism, the formation of 9 is proposed to proceed via in-... 

Friedrichsen and co-workers (133) approached substituted benzotropolones from an aromatic substituted carbonyl ylide with a tethered alkyne as the intramolecular dipolarophUe (Scheme 4.67). Starting from an aromatic anhydride, Friedrichsen was able to make the tethered alkyne via addition of either pentyn-ol or hexyn-ol, then transform the recovered benzoic acid to the a-diazocarbonyl cycloaddition precursor. Addition of rhodium acetate resulted in the tandem formation of cyclic carbonyl ylide followed by cycloaddition of the tethered alkyne producing the tricyclic constrained ether 252. Addition of BF3 OEt2 opened the ether bridge, forming the benzotropylium ion, which subsequently rearranged to form the tricyclic benzotropolone (253). 

The congeners of 243 and 244 are also formed by the reaction with either Mc2PhSiH or Et2MeSiH (13 silane > 2 1) 243 is readily protodesilylated during purification to give 2,4-diphenylcyclopent-2-enone. When 13 is replaced by 1-hexyne, a product akin to 244 is produced as a major cyclocarbonylation product. At higher temperatures, various types of carbonylation products are produced (Equation (43)). ... 

Chemoselective cocycloaddition of two molecules of a terminal alkyne together with one molecule of an internal alkyne into a benzene product is possible due to the relative unreactivity of phosphine nickel carbonyls towards simple trimerization of the internal alkyne itself (equation 28). ° " Careful control of reaction conditions has also permitted selective intermolecular cocycloaddition in the presence of cobalt catalysts as well for example, diphenylacetylene and 3-hexyne give rise to a 57% yield of 1,2,3,4-tetra-pheny 1-5,6-diethylbenzene. ... 

The reaction between acetylenes and ruthenium carbonyls produces a series of n complexes with cyclic ligands which, as in the iron system, have either the metal or a CO group incorporated into the ring. Accordingly, 3-hexyne 536) and hexafluoro-2-butyne 90) react with Ru3(CO)i2 to give the (substituted cyclopentadienone)tricarbonylruthenium complexes with structures presumably comparable to those of the iron complexes (93-95). Although diphenylacetylene will not react directly with Ru3(CO)i2 to produce this type of complex 536), it can be prepared 90) by treating Ru3(CO)i2 with tetracyclone in benzene under reflux. 

Carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (87) in ethanol containing hydrochloric acid (5%) affords diethyl diisopropylidenesuccinate (89) (Scheme 11-26). The reaction is explained by the Pd(0)-catalyzed dicarbonylation to give 88, and subsequent elimination of water to give 89 [11]. 

Alkyne cyclotrimerization occurs at various homogeneous and heterogeneous transition metal and Ziegler-type catalysts [7], Substituted benzenes have been prepared in the presence of iron, cobalt, and nickel carbonyls [8] as well as trialkyl- and triarylchromium compounds [9]. Bis(acrylonitrile)nickel [10] and bis(benzonitrile)palladium chloride [11] catalyze the cyclotrimerization of tolane to hexaphenylbenzene. NiCl2 reduced by NaBH4 has been utilized for the trimer-ization of 3-hexyne to hexaethylbenzene [12]. Ta2Cl6(tetrahydrothiophene)3 and Nb2Cl6(tetrahydrothiophene)3 as well as 7 -Ind-, and 77 -Ru-rhodium... 

Dotz and coworkers prepared several interesting and novel glycosylidene carbenes (259-261) by reaction of lithiated glycal 258 with the appropriate metal carbonyl derivative. The synthetic utility of the formed carbenes was demonstrated by reaction with 3-hexyne to give a mixture of complexed and uncomplexed adducts 262 and 263, respectively. The anomeric chromium carhene 264 was converted to 265 hy exposure to ethoxy ethyne (Scheme 48) [70]. The same workers have carried out a similar chromium-mediated henzannulation (266 —> 268), this time with the chromium on the aromatic fragment [71]. Other sugar-hased carhenes have also been prepared [72]. 

The complex [(OC)4Fe(//-PPh2)Pd( -Cl)]2 is a selective catalyst for the isomerization of 1-octene to 2-octene and the hydrogenation of 1-hexyne in the presence of 1-hexene. At 448 K, under 100 atm H2, 93% of a sample of 1-hexyne in benzene was reduced to hexene and only 3% to hexane. This is unexpected because palladium is usually an excellent catalyst for the hydrogenation of olefins. It also catalyzes the carbonylation of 1-octene under mild conditions (348 K, 50 atm). The total yield of esters was ten times greater than with [PdCl2(PPh3)2] as a catalyst. This bimetallic complex was also an effective catalyst for the carbonylation of 1,5-cyclooctadiene. ... 

To avoid the polymerization initiated by abstraetion of the a-hydrogen atom, Ramehandran et al. have foeused their attention on aryl tiifluoromethyl ketones. By eonsidering the match between the reactivities of the olefin and carbonyl partners, they succeeded in accomplishing the MBH reaction between moderately reactive electrophile e.g. trifluoroacetophenone, trifluoroacetylthiophene, 3-tiifluoroacetyl-indole, 2-chloro-2,2-difluoroacetophenone, 1,1,1 -trifluoro-4-phenyl-3-butyn-2-one and 4,4,5,5,6,6,6-heptafluoro-l-phenyl-l-hexyn-3-one) with moderately reactive olefins e.g. ethyl acrylate and acrylonitrile) in the presence of DABCO in high yields (Chapter 2.2.1). ... 

The first Rh-catalyzed carbonylative silylcarbocyclization (CO-SiCaC) was reported in 1992 in which silylcyclopentenone 531 was isolated as a minor product in the silylformylation of 1-hexyne 530 (Scheme 2-79). 

Scheme 2-79. Rh-catalyzed carbonylative silylcarbocyclization (CO-SiCaC) of 1-hexyne 530.

A mixture of 3-hexyne, chloracetonitrile, sodium cobalt carbonylate, and dicyclohexylethylamine in ether allowed to stand overnight in a flask filled with CO at 25° and connected to a gas buret 2,3-dielhyl-5-cyano-2,4-penta-dieno-4-lactone. Y 62%. F. e. s. R. F. Heck, Am. Soc. 86, 2819 (1964). 

When 1-hexyne is treated with a catalytic amount of sulfuric acid in an aqueous solvent, initial reaction with the acid gives the expected secondary vinyl carbocation 103, and the most readily available nucleophile in this reaction is water (from the aqueous solvent). Nucleophilic addition of water to 103 leads to the vinyl oxonium ion 104. Loss of a proton in an acid-base reaction (the water solvent is the base) generates a product (105) where the OH unit is attached to the C=C unit, an enol. Enols are unstable and an internal proton transfer converts enols to a carbonyl derivative, an aldehyde, or a ketone. This process is called keto-enol tautomerization and, in this case, the keto form of 105 is the ketone 2-hexanone (106). (Enols are discussed in more detail in Chapter 18, Section 18.5.) Note that the oxygen of the OH resides on the secondary carbon due to preferential formation of the more stable secondary carbocation followed by reaction with water, and tautomerization places the carbonyl oxygen on that same carbon, so the product is a ketone. When a disubstituted alkyne reacts with water and an acid catalyst, the intermediate secondary vinyl cations are of equal stability and a mixture of isomeric enols is expected each will tautomerize, so a mixture of isomeric ketones will form. 

Draw both enol products expected when 5-methyl-2-hexyne is treated with an acid catalyst in aqueous THF. Also draw the carbonyl products expected from both enols. 

---