Lithium trimethylsilylacetylide

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Lithium-Ethylamine, 158 Lithium o-lithiophenoxide, 166 Lithium methoxyacetylide, 166 Lithium phenylacetylide, 244 Lithium trialkylzincates, 221 Lithium trimethylsilylacetylide, 206 Lithium trimethyl(tributylstannyl)-aluminate, 320... 

Nucleophilic addition of lithium trimethylsilylacetylide (49) to C60 to produce the adduct 50 (equation 18) was reported by Diederich and coworkers28. The structure of... 

The first issue confronted by Myers was preparation of homochiral epoxide 7, the key intermediate needed for his intended nucleophilic addition reaction to enone 6. Its synthesis began with the addition of lithium trimethylsilylacetylide to (R)-glyceraldehyde acetonide (Scheme 8.6).8 This afforded a mixture of propargylic alcohols that underwent oxidation to alkynone 10 with pyridinium dichromate (PDC). A Wittig reaction next ensued to complete installation of the enediyne unit within 11. A 3 1 level of selectivity was observed in favour of the desired olefin isomer. After selective desilylation of the more labile trimethylsilyl group from the product mixture, deacetalation with IN HC1 in tetrahydrofuran (THF) enabled both alkene components to be separated, and compound 12 isolated pure. 

Enantloselective ethynylation of benzaldehyde, The reaction of benzaldehyde with lithium trimethylsilylacetylide in the presence of 1 in DME affords the corresponding (S)-alkynyl alcohol 2 in 92% optical yield. The optical yield is —75% with lithium acetylide itself. 

Compound 246 was prepared in a yield of 83% by treating lithium trimethylsilylacetylide with tellurium and carbon diselenide followed by water in the final step <2001JMC2431>. 

The 1,3-ditellurole derivative 149 was prepared from trimethylsilylacetylene according to Equation (60) <20020L2581>. Thus, lithium trimethylsilylacetylide was reacted with tellurium, whereupon the resulting tell-urolate was protonated to give 149. This compound suffered extensive decomposition during purification and could not be desilylated. Instead, it was subjected to Vilsmeier-Haack formylation giving a stable dialdehyde 150 (Equation 22). 

In the laboratory of E.J. Corey, the first synthesis of nicandrenones (NIC), a structurally complex steroid-derived family of natural products, was accomplished. The side chain of NIC-1 was constructed from the known six-membered lactone which was converted to the Weinreb s amide by treating it with excess MeNH(OMe) HCI and trimethyl-aluminum. The resulting primary alcohol was protected as the TBS ether. The ethynylation of this amide was carried out by reaction with two equivalents of lithium trimethylsilylacetylide to afford an ynone, which was reduced enantioselectively to the corresponding propargylic alcohol using CBS reduction. 

Furthermore, optically active alkynyl alcohols, useful intermediates for the synthesis of several optically active natural products, were obtained by the asymmetric addition of lithium acetylides to aldehyde in the presence of chiral ligand 2a Enhanced enantioselectivity in this reaction depends apparently on the substituent group in the acetylene moiety. As shown in Table 8, use of trialkylsilylacetylides gave the best results Various optically active ethynyl alcohols were obtained by the reaction of lithium trimethylsilylacetylide with aliphatic aldehydes, as summarized in Table 9... 

Table 9. Enantioselective Addition of Lithium Trimethylsilylacetylide to Aliphatic Aldehydes ...

The synthesis of diethyl ethynylphosphonate has recently been described using lithium few(diisopropyl unino)boracetylide as a synthetic equivalent for lithium acetylide. After reaction with diethyl chlorophosphate in THF at -TS C, the protected diethyl ethynylphosphonate is hydrolyzed with a 3 M1 ICl solution to produce diethyl ethynylphosphonate in good overall yield (72%), comparable with those previously obtained (Scheme I.IO). Synthesis of diethyl ethynylphosphonate has also been reported with an overall yield of 68% by a three-step synthesis including the reaction of lithium trimethylsilylacetylide with diethyl chlorophosphite (83%) followed by oxidation with MCPBA and deprotection with KF in EtOH (82%). ... 

Preparative Method by treatment of trimethylsilylacetylene with copper(I) t-butoxide, by addition of CuBr SMe2 to a THF solution of lithium (trimethylsilylacetylide, or by treatment of trimethylsilylacetylene with triethyl phosphite and copper(I) chloride. ... 

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