3-stannylated pyrroles

The Pd-catalyzed cross coupling reaction of 3-stannylated pyrroles is also known. Muchowski has thus prepared and utilized 96 to effect Stille couplings leading to 97 [59]. 

Although the stannylated pyrroles are normally obtained via lithiation, two other methods to prepare these Stille precursors have been devised. Caddick has found that the addition of tri-n-butylstannyl radical to pyrrole 82 affords stannylpyrrole 83 in good yield [68],... 

Yu and co-workers [92,93] have prepared conjugated polymers exhibiting liquid crystallinity by allowing 2,5-bis(tributylstannyl)thiophene to react with aryl diodides or ditriflates, while van Haare et al. [94] have obtained oligomers containing thiophene and pyrrole units, starting from a stannylated pyrrole derivative. 

Single and double coupling reactions involving stannylthiophenes (and -pyrroles) with dibromoquinones have been reported [88] another less conventional substrate used was a 2,6-dibromophosphosphabenzene (Scheme 4-30 here also single and double couplings were reported, as was the coupling of a 2-stannyl-pyridine) [89]. 

Pyrroles. The general synthesis of substituted pyrroles by the [3+2]cycloaddition pathway involving TOSMIC and conjugated carbonyl compounds has been extended to 3-arenesulfonylacrylic esters. C-stannylation prior to the cycloaddition enables the preparation of pyrroles containing a stannyl substituent at C-2 ... 

Pyrrole,110 imidazoles, and 1,2,4-triazoles 111 are readily stannylated on nitrogen, but the products are better considered as stannylamines (Section 16.1) rather than heteroaromatic derivatives. The only route as yet to C-stannylpyrroles with an unblocked NH group appears to be by cycloaddition (see above). 

Useful alternative preparations of stannanes include palladium-catalysed decarboxylation of stannyl esters. ° Trialkylstannyl and trialkylsilyl anions are highly reactive and will displace halogen without the use of a catalyst. It is possible to directly silylate indoles and pyrroles via electrophilic substitution. ... 

Boc-pyrrole has been coupled both through the 2-boronic acid derivative and the 2-trimethyl-stannyl derivative, both of which can be prepared from the lithiopyrrole <91S613>. Cross-coupling of l-Boc-2,5-dibromopyrrole with l-Boc-2-trimethylstannylpyrrole gave a tripyrrole (Scheme 129) <91SM403>. 

Example 8 Stifle CrosscoupUng Polymerization of 1,2-Bis(tributyl-stannyl)ethylene (13) with 4,6-Diiodo-5-methyl-2-(4,5-bis(hexylthio)-l,3-dithiole-2-ylidene)-5H- l,31dithiolo) 4,5-c pyrrole (14) to give P17 ... 

Perfect 2,5-linked polypyrrole is prepared by using Stille chemistry [39]. t-BOC-protected pyrroles are converted into bromo-trimethyl stannyl monomers and subsequently polymerized using a Pd-catalyst. Although of relative low molecular weight (Af = 3400), the fully characterized protected polypyrrole can be converted to perfect polypyrrole by thermal deprotection, (Scheme 10.3). 

Fig. 25 Synthesis of pyrrole containing copolymer via Stille coupling of 2,5-bis(5-(trimethyl-stannyl)-2-thienyl)-Af-dodecylpyrrole and 4,7-dibromo-2,l,3-benzotliiadiazole...

---