Sonogashira conditions

The indole compound was described by Flynn et al. [73] and is prepared in a similar manner as the thiophene 103 and furan 108. One method involved a similar synthesis as described in Scheme 25, using the relevant starting material. However, an alternative synthesis involved a one-pot, room-temperature synthesis, Scheme 27. The o-iodotrifluoroacetanilide 110 was coupled to the alkyne 111 under Sonogashira conditions in MeCN. K2CO3 and the aryliodo compound 107 was added and the reaction stirred to produce the protected product 112 with a 77% yield. Deprotection to the corresponding phenol 113 was performed using AICI3. 

Quite different from the original Sonogashira conditions, the following cross-coupling was achieved under the Jeffery s ligand-free conditions in the absence of cuprous iodide [63] [64]. 

Muchowski has utilized Af-TIPS-3-iodopyrrole to prepare a series of 3-alkynyl pyrroles 119 using standard Sonogashira conditions [59]. Pyrroles 120 were obtained after fluoride cleavage of the TIPS group. Similarly, 3,4-bis(alkynyl)pyrroles were prepared from N-TIPS-3,4-diiodopyrrole [59]. 

Pyrrole 151 can be thallated [110] and subjected to Heck (and Sonogashira) conditions to afford the anticipated products 152 [111]. 

Scheme 8.5 Alkyne metathesis reactions of polymer 35 prepared from the (a) Sonogashira condition and (b) hexacycle 36 and diphenylacetylene [35].

Using Sonogashira conditions, the (R)-acetylenes (R)-904 and (R)-905 were coupled with M-carbethoxy-2-iodoaniline 700 to afford the aryl acetylenes (R)-906 and (R)-907. Executing similar functional group transformations as reported... 

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... 

Iodouracil derivatives are particularly reactive under normal Sonogashira conditions, as demonstrated by the room temperature synthesis of 5-ethynyluracil (eniluracil) 256 from trimethylsilylacetylene 254 and 5-iodouracil 255 <2006GJC580>. 

In the context of a coupling-1,3-dipolar cycloaddition sequence, Muller and coworkers [89] developed a consecutive one-pot, three-component process to indolizines. Starting from (hetero)arenecarbonyl chlorides 88 and terminal alkynes 89 under Sonogashira conditions, the expected alkynones were formed (Scheme... 

The syntheses of other dimers are also illustrated in Scheme 6. Thus, treatment of 2-propynyl a-D-mannopyranoside 10 with diiodobenzene (para isomer illustrated) under the optimum Sonogashira conditions described above provided 30 that after deprotection gave 31 in quantitative yield. For comparison purpose, dimer 36 and 38 (29) were prepared from peracetate 32 using bisphenol A (33) and 2-butyne-l,4-diol (34) under Lewis acid conditions (Scheme 7). 

The distinctive feature of the catalytic generation of alkynones under modified Sonogashira conditions is the usage of one stoichiometrically necessary equivalent of triethylamine per bond forming reaction [47, 48]. Since the base is inevitably consumed in binding the liberated hydrogen halide the reaction medium is... 

Muller and coworkers have recently developed a coupling-isomerization reaction, initially identified as a side reaction which occurred under standard Sonogashira conditions [79]. As demonstrated below, the coupling reaction is followed by a shuffling of oxidation states via an alkyne-allene isomerization [80]. The product, a,P-unsaturated ketone 146, is reminiscent of a product which would be obtained from a Heck reaction. The utility of this reaction was further demonstrated when diamine 147 was added to the reaction pot. Following a conjugate addition reaction and imine formation, compound 148 resulted from the three-component, one-pot reaction sequence enabled by the coupling-isomerization reaction. 

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