Alkynylations, carbonyl

An earlier review treated the organometallic derivatives, including alkyl, aryl, vinyl, alkynyl, carbonyl, carbene, alkene and alkyne complexes,16 and these will not be treated here (see Table 1 for other books and reviews on organogold chemistry). Two important articles dealing with [AuCl(CO)], including its structure and catalytic properties, have been published recently.97,381... 

A study of the role of base and ligand in the isomerization of manganese-coordinated conjugated alkynyl carbonyls to the corresponding allenyl carbonyls shows that manganese requires a ligand prior to isomerization with amine bases and the efficacy of these bases correlates with p Ka (Scheme 97). Potassium /-buloxide led to rapid isomerization in the absence of added ligand.140... 

An example in which the chemoselective photoaddition of carbonyl compounds to a conjugated enyne becomes an important issue has been reported by Carless. A solution of 2-methylbut-l-en-3-yne and benzophenone was irradiated to form in 58% yield the oxetane (76), which was converted under acid catalysis to conjugated enyne (77). Surely the synthetic utility of such a process, as well as further applications of alkynyl-carbonyl photocycloadditions, will be forthcoming. 

If an alkynyl carbonyl is used, some useful allenyl derivatives are prepared [Eq. (46) ... 

Other synthetic approaches involve cyclocondensations of hydroxylamine with 1,3-bielectrophiles. For instance, starting from conjugated alkynyl-carbonyl compounds 14, electrophilic cyclization allowed a facile access to a variety of 3,5-disubstituted-4-halo(or seleno)isoxazoles 16 in high yields under mild reaction conditions, by treatment of 0-methyl oximes 15 with ICl, I2, Br2, or PhSeBr <050L5203>. 

The use of both LIU and HIU has been shown to increase the efficiency of the P-K reaction, which involves the formation of cyclopentenone from the annulation of a cobalt alkynyl carbonyl complex and an alkene. The use of low-power ultrasound, as for example, from a cleaning bath, although capable of producing intramolecular P-K reactions, generated relatively low cyclization yields. The motivation for the use of high intensity came from its ability, as previously described, to effectively decarbonylate metal carbonyl and substituted metal carbonyl complexes. Indeed, HIU produced by a classic horn-type sonicator has been shown to be capable of facile annulation of norbornene and norbornadiene in under 10 min in the presence of a trimethylamine or trimethylamine N-oxidc dihydrate (TMANO) promoter, with the latter promoter producing cleaner product mixtures. This methodology also proved effective in the enhancement of the P-K reaction with less strained alkenes such as 2,5-dihydrofuran and cyclopentene, as well as the less reactive alkenes -fluorostyrene and cycloheptene. The mechanism has been postulated to involve decarbo-nylation of the cobalt carbonyl alkyne, followed by coordination by the amine to the vacant coordination sites on the cobalt. 

SCHEME 5.24 Synthesis of Al-containing heterocyclic ring systems by coupling of FCC VI with an n-alkynyl carbonyl heteroaryl 28-30 and a dienophile. 

G. P. Jana, S. Mukherjee, B. K. Ghorai, Synthesis 2010, 3179-3187. Multicomponent approach for the synthesis of phenanthridine and acridine ring systems via the coupling of Fischer carbene complexes with heteroaromatic o-alkynyl carbonyl derivatives. 

Using less polar, hexane-based solvent mixture, more readily available alkynyl allylic alcohols can also be isomerized to the corresponding furans upon exposure to 10% AgN03 on silica. Extension of this approach to alkynyl bromopropenoic acids allows formation of a-bromo lactones suited for further cross-coupling reactions. Cyclization of a-alkynyl carbonyl substrates proved to be an efficient method for the preparation of substituted fura-nopyrimidine nucleosides (eq 13). ... 

As shown in Sections 9.4.1 and 9.4.2, electron-deficient and coordinating alkynyl carbonyl compounds showed high reactivity in cationic rhodium(I)/biaryl bispho-sphine complex-catalyzed enantioselective [2- -2-1-2] cycloaddition. Therefore, Tanaka et al. investigated the use of alkynylphosphonates or alkynylphosphine oxides instead of alkynyl carbonyl compounds for the practical synthesis of axially chiral biaryl phosphorus compounds. The enantioselective [2- -2-1-2] cycloadditon... 

Finally (d + aV dditions of 1-alkenyl and 1-alkynyl anions to carbonyl groups should be mentioned. Examples are the addition of vinylmagnesium bromide to ketones e.g. in the first step of Torgov s steroid synthesis (I.N. Nazarov, 1957), and the famous alkynylation of... 

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

The carbonylation of aryl iodides in the presence of terminal alkynes affords the acyl alkynes 565. Bidentate ligands such as dppf give good results. When PhjP is used, phenylacetylene is converted into diphenylacetylene as a main product[4l5]. Triflates react similarly to give the alkynyl ketones 566[4I6], In... 

In addition to alcohols, some other nucleophiles such as amines and carbon nucleophiles can be used to trap the acylpalladium intermediates. The o-viny-lidene-/j-lactam 30 is prepared by the carbonylation of the 4-benzylamino-2-alkynyl methyl carbonate derivative 29[16]. The reaction proceeds using TMPP, a cyclic phosphite, as a ligand. When the amino group is protected as the p-toluenesulfonamide, the reaction proceeds in the presence of potassium carbonate, and the f>-alkynyl-/J-lactam 31 is obtained by the isomerization of the allenyl (vinylidene) group to the less strained alkyne. 

The allenyl moiety (2,3-aikadienyl system) in the carbonylation products is a reactive system and further reactions such as intramolecular Diels-Alder and ene reactions are possible by introducing another double bond at suitable positions of the starting 2-alkynyl carbonates. For example, the propargylic carbonate 33 which has l,8(or 1.9)-diene-3-yne system undergoes tandem carbonylation and intramolecular Diels-Alder reaction to afford the polycyclic compound 34 under mild conditions (60 C, 1 atm). The use of dppp as ligand is important. One of the double bonds of the allenyl ester behaves as part of the dieneflSj. 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

An indium chloride-catalyzed coupling of alkynes to aldehydes was also possible in giving a, (J>-unsaturatcd carbonyl compounds in water in low yields (Eq. 8.88).223 (Alkynylation is discussed in Chapter 4 on alkynes.)... 

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