TIPS-acetylene

Scheme P12.3.2 Outline for the synthesis of o -(TIPS-acetylene)-a -azide terminated polystyrene. (Drawn following the synthesis method of Opsteen and Van Hest, 2007.)...

Alternate Name TIPS-acetylene triflone or TIPS-ethynyl triflone. Solubility most aprotic organic solvents. 

Transition Metal-catalyzed Coupling Reactions. TIPS-acetylene has been widely used for transition metal-catalyzed coupling reactions with a variety of aryl-X and vinyl-X (X = 1, Br, Cl, and OTf) compounds as useful electrophiles in the presence of proper cocatalysts or additives, leading to the corresponding ethynyl-functionalized derivatives. 

Treatment of TIPS-acetylene with aryl (eq 1) and vinyl halides (eqs 2 and 3) and triflates (eq 4) and an appropriate Pd(0) catalyst (Sonogashira coupling) in the presence of copper(l) as cocatalyst affords arylalk3mes and enynes in good 3ueld. 

Synthesis of Polyynes. Conjugated diyne and polyyne units, which exhibit unusual electrochemical, optical, and structural properties, can be efficiently constructed from 1-haloalkynes via homologation by one acetylene unit with TIPS-acetylene through a transition metal-catalyzed cross-coupling reaction, 2 which allows an access to a new class of polyyne framework. 

The copper-catalyzed cross-coupling of TIPS-acetylene with bis iodo 1,6-heptadiyne generated a triisopropylsilyl-capped tetrayne in good yield (eq 15). ... 

Transition Metal-catalyzed Cross-addition of TIPS-acetylene to Alkynes. Transition metal-catalyzed coupling reaction of a bulky silyl-substituted terminal alkyne through the addition of the C-H bond to carbon-carbon triple bonds can lead... 

Inoue and coworkers reported that dinuclear and mononu-clearpalladium complexes possessing Al,Al -bis[2-(diphenylphos-phino)phenyl]amidate (DPFAM) as a multidentate ligand were effective as catalysts for the selective cross-addition of TIPS-acetylene to a variety of internal and terminal alkynes (eq 18). ... 

Nickel-catalyzed three-component cross-trimerization has also been carried out in a highly chemo-, regio-, and stereoselective fashion. The 1 2 cross-trimerization involving TIPS-acetylene (eq IQ) and two internal alkynes and the 1 1 1 three-component cross-trimerization (eq 20) of three distinct alkynes in the presence of [Ni(cod)2] and a phosphine ligand afford the corresponding TIPS-substituted l,3-diene-5-ynes in good yield with a high selectivity. 

For a three-component reaction, Ogata and Fukuzawa demonstrated that one molecule of TIPS-acetylene was hydroalkynylated to a second molecule of TIPS-acetylene via Ni(0) catalysis and the adduct was nicely intercepted by norbornenes to furnish a series of elaborated norbornanes (eq 24). ... 

Direct Alkynylation. Ni-catalyzed direct alkynylation on azoles has been achieved without assistance of halogen-mediated activation by using oxygen as oxidant in the catalytic cycle. TIPS-acetylene was added to a variety of nonhalogenated azoles to produce the Sonogashira coupling products (eq 25). ... 

For direct alkynylation with TIPS-acetylene, a hypervalent iodine TIPS-acetylene reagent can also be used as demonstrated in Waser s recent works. Alkynylation on C-3 of indole was catalyzed by AuCl (eq 26) and the Wacker cyclization s intermediate was intercepted by the hypervalent iodine TIPS-acetylene (eq 27).2 ... 

Conjugate Addition. Catalytic asymmetric conjugate addition of acetylenes to a. -unsaturated carbonyl confounds is one of the most challenging tasks in organic chemistry and TIPS-acetylene has been used as a useful tool reagent to confirm the viability of the developed protocols. Rh(I)-catalyzed conjugate alkynylation has been extensively developed by Hayashi and coworkers. Asymmetric conjugate addition of TIPS-acetylene was accomplished via a Rh(T) catalysis (eq 28) and the effects of the alkyl substituents on the sUylacetylenes were examined for their... 

The dimerization of TIPS-acetylene in the Rh-catalyzed conjugate addition can be further minimized by employing the TIPS-acetylene elaborated with an alkynylsilanol group and an improved reaction protocol (eq 30). In the same report, this new protocol was applied to conjugate alkynylation of cyclic enones (eq31). 

In a different context, Nishimura, Hayashi and coworkers demonstrated an asymmetric ring-opening alkynylation of aza-benzonorbornadienes using TIPS-acetylene, which was superior to other acetylenes in yield and stereoselectivity (eq 32). 

Cycloaddition. A cobalt-catalyzed system has delivered highly efficient and regioselective Diels-Alder cycloadditions between trialkylsilylacetylenes and 1,3-dienes. TIPS-acetylene was equally effective as other silylacetylenes (TMS-, TES-, TPS-) for the Diels-Alder reaction with isoprene (eq 33). ... 

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