Bis tributylstannyl acetylenes

Dipolar cycloaddition reaction of trimethylstannylacetylene with nitrile oxides yielded 3-substituted 5-(trimethylstannyl)isoxazoles 221. Similar reactions of (trimethylstannyl)phenylacetylene, l-(trimethylstannyl)-l-hexyne, and bis (trimethylsilyl)acetylene give the corresponding 3,5-disubstituted 4-(trimethyl-stannyl)isoxazoles 222, almost regioselectively (379). The 1,3-dipolar cycloaddition reaction of bis(tributylstannyl)acetylene with acetonitrile oxide, followed by treatment with aqueous ammonia in ethanol in a sealed tube, gives 3-methyl-4-(tributylstannyl)isoxazole 223. The palladium catalyzed cross coupling reaction of... 

Interestingly, the alkyne-oxazole Diels-Alder cycloaddition strategy provides a unique entry to some furyl stannanes [52]. Thus, thermolysis of bis(tributylstannyl)acetylene (50) and 4-phenyloxazole (51) led to a separable mixture of 3,4-bis(tributylstannyl)furan (52, 19% yield) and 3-tributylstannylfuran (53, 23% yield). 

Dihydro allyl adducts like (254) are obtained by reaction of thiazoles with allyltributyl tin in the presence of alkyl chloroformates acting as activators of the thiazole ring (Scheme 28) (94JOC1319). This reaction most likely takes place via the intermediate azolium salt. Under these conditions even organolithium compounds can add to thiazoles (84TL3633). Similarly, direct ethynylation of thiazole and benzothiazole can be achieved by reaction with bis(tributylstannyl)acetylene (Scheme 29) (94SL557). 

The preparation of the symmetrical alkyne 14 is accomplished by a double Stille coupling of two molecules of aryl bromide 13 with 1,2-bis(tributylstannyl)acetylene (23) in the presence of catalytic amounts ofPd(PPh3)4. ... 

The remaining fraction of the mixture after distillation was bis-(tributylstannyl )acetylene which could be recycled for the preparation of tributylethynylstannane. 

Ethynylation of pyridazine and phthalazine could be achieved using bis(tributylstannyl)acetylene via A -alkoxycarbonyl quartemary salts of the substrates, followed by treatment with trifluoroacetic acid [94MI557]. Reaction of pyridazines 26 with allyltributyltin have been found to afford 4-allyl... 

The same methodology has also been applied to the synthesis of stannylated furans. Heating bis(tributylstannyl)acetylene and 55 in a sealed mbe at 185°C for 10 days provided 3,4-bis(tributylstannyl)furan 139 and 3-(tributylstannyl)furan 140 in 22 and 10% isolated yield, respectively (Fig. 3.41). These stannanes underwent palladium-catalyzed couplings with aryl, vinyl, and benzylic halides as well as acid chlorides. 

Phthalazine with bis(tributylstannyl)acetylene and ethyl chlorofonnate gave ethyl l-ethynyl-l,2-dihydro-2-phthalazinecarboxylate (70) (substrate, Bu3SnC=CSnBu3, CH2CI2, ClC02EtJ. dropwise, 0°C 20°C, <3 days then F3CC02Hi, 20°C, 30 min 82%). - ... 

Bis(9-borabicyclo[3.3.1]nonyl)acetylene is rapidly prepared [39] in situ, utilizing neat bis(tributylstannyl)acetylene and 2 equiv of 9-bromo-9-BBN at -78 °C. The reagent is an effective dienophile and undergoes reactions with simple acyclic dienes at 110 °C. The 1,4-cyclohexadienes are obtained in good yields after debromination of the Diels-Alder adducts with acetic acid (Chart 30.6) [39]. 

Poly(p-pyridyl vinylene)s with random (equation 110) and with head-to-head (equation 111) couplings of the pyridyl units were synthesized by the Stille reaction (205). Soluble poly(l,4-phenyleneethynylene)s were prepared by the Pd(0) catdyzed cross-coupling of bis(tributylstannyl)acetylene with 2,5-dialkoxy-1,4-dibromobenzenes. (equation 112) (208)... 

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