Cadiot-Chodkiewicz

It was found [99JCS(PI )3713] that, in all cases, the formation of the deiodinated products 38 and 39 was accompanied by formation of the diynes 40 which were isolated in 60-90% yield. The authors believed that the mechanism of deiodination may be represented as an interaction ofbis(triphenylphosphine)phenylethynyl-palladium(II) hydride with the 4-iodopyrazole, giving rise to the bisftriphenylphos-phine)phenylethynyl palladium(II) iodide complex which, due to the reductive elimination of 1 -iodoalkyne and subsequent addition of alk-1 -yne, converts into the initial palladium complex. Furthermore, the interaction of 1-iodoalkynes with the initial alkyne in the presence of Cul and EtsN (the Cadiot-Chodkiewicz reaction) results in the formation of the observed disubstituted butadiynes 40 (Scheme 51). 

Propiolaldehyde diethyl acetal has found numerous synthetic applications in the literature which may be briefly summarized. The compound has been utilized in the synthesis of unsaturated and polyunsaturated acetals and aldehydes by alkylation of metal-lated derivatives, " by Cadiot-Chodkiewicz coupling with halo acetylenes, " and by reaction with organocuprates. Syntheses of heterocyclic compounds including pyrazoles, isoxazoles, triazoles, and pyrimidines have employed this three-carbon building block. Propiolaldehyde diethyl acetal has also been put to use in the synthesis of such natural products as polyacetylenes " and steroids. ... 

The conversion of the dehydrotrimer 135 into the corresponding bis-cuprate followed by coupling with dibromide 131 (Cadiot-Chodkiewicz conditions) gave the expanded [5]pericycline 122 in 53% isolated yield (Scheme 28) [4]. The more versatile approach by simple oxidative cyclooligomerization of dehydrooligomers of type 135 under high dilution conditions as shown in Scheme 28 provided the acetylene-expanded [3]- 82, [5]- 122 and [6]pericyclines 163 in reasonable to excellent yields [4,7]. 

The oxidative coupling, however, normally provides better results, as was demonstrated by the reasonably efficient cyclization of 179 to the homoconjugated 16-membered macrocycle 180 (14% yield) with alternating ethyne and butadiyne units (Scheme 34) the alternative Cadiot-Chodkiewicz coupling of the bisterminal diyne 38 and the dibromotriyne 177 gave only a 2.6% yield of 180 [4]. 

The dimerization of terminal alkynes, known as the Glaser coupling, the Eglinton coupling, and the Cadiot-Chodkiewicz coupling, is one... 

Later, Jones et al. applied this Cadiot-Chodkiewicz coupling reaction to the synthesis of triynoic acid, a fungal polyacetylene (Eq. 4.21).41... 

Recently, Marino et al. reported a Cadiot-Chodkiewicz cross-coupling reaction of bulky trialkylsilyl-protected alkynes with 1-bromoalkynes in aqueous amine to form a variety of unsymmetrical diynes in good yields (75 95%) (Eq. 4.23).44... 

The scope of the SH reaction encompasses sp-sp2 (alkenyl, aryl (29),143 heteroaryl) and sp-sp couplings (the modified Cadiot-Chodkiewicz reaction).142 Iodides are most frequently used as electrophilic coupling partners, though the use of bromides, triflates (30),144 or even some reactive chlorides (31)145 is also possible. Due to the low steric bulk of the acetylenic unit, as well as its exceptional ability in the transduction of electronic effects, the SH reaction is well suited for construction of new (e.g., star-like) molecular architectures through polysubstitution (32).146... 

The monomer used in our studies was synthesized by Cadiot-Chodkiewicz Coupling (14) of 1-iodooctadecyne and 10-Undecynoic acid. 10 Undecynoic acid was used as received from Farchan Labs... 

Aryl-acetylene synthesis, Cf. Cadiot-Chodkiewicz coupling and Sonogashira coupling. The Castro-Stephens coupling uses stoichiometric copper, whereas the Sonogashira variant uses catalytic palladium and copper. 

An alternative mechanism similar to that of the Cadiot-Chodkiewicz coupling ... 

The two reactions described above can be applied for the synthesis of symmetrical few-acetylenes only. Unsymmetrical bis-acetylenes can be prepared by using the Cadiot-Chodkiewicz reaction. For that method a terminal alkyne 1 is reacted with a bromoalkyne 8 in the presence of a copper catalyst, to yield an unsymmetrical coupling product 9 ... 

This side-reaction is most serious in the case of acetylenes RC=CH with a relatively low acidity aliphatic 1-alkynes, e.g. 1-octyne, and acetylenic alcohols HCaC(CH2)nOH with n > 2, give reduced yields (40-50%) in the coupling reaction. In many other reactions, yields are high. Since the bromoalkyne usually has the highest "added value", economical considerations prescribe the use of an excess of the free acetylene, especially when it is inexpensive, e.g. propargyl alcohol. The mechanism of the Cadiot-Chodkiewicz reaction has not been studied in detail, but is seems likely that a copper acetylide ROCCu is formed first it often appears as a yellowish suspension. 

Z,Z-C2H5SCH=CHCH=CHCaC-r-Bu (undistilled) is obtained from Z-C2HjS--CH CHC=CCsC-t-Bu by a similar procedure (1 h reflux). The starting compound is prepared by Cadiot-Chodkiewicz coupling of Z-CjHjSCf CHGsCH with BiO C-t-Bu... 

R = alkyl, aryl 2. ROCBr + HOeCCH2OH. Cadiot-Chodkiewicz 213... 

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