Silyl propargylation

The combined solutions were dried over magnesium sulfate and subsequently concentrated in a water-pump vacuum. Distillation of the residue through a 30-cm Vigreux column gave the silylated propargyl sulfide, b.p. 65°C/18 mmHg, n ... 

The Stille adduct of 2-bromothiophene and l-ethoxy-2-tributyl-n-stannylethene or 1-ethoxy-l-tri-n-butylstannylethene is a masked thienyl aldehyde or a masked ketone, respectively [77-80]. Vinylstannane 93, derived exclusively as the -isomer from hydrostannation of bis(trimethyl-silyl)propargyl amine (92), was coupled with 2-bromothiophene to form ( )-cinnamyl amine 94 upon acidic hydrolysis [81, 82], In another case, stereoisomerically pure phenyl ( )-2-tributylstannyl-2-alkenoate 95, arising from Pd-mediated hydrostannation of phenyl ( )-2-alkynoate, was joined with 2-iodothiophene to deliver the stereodefmed trisubstituted a,p-unsaturated ester 96 [83, 84],... 

Silyl propargyl alcohols, XC=CSiMe2R [X=RiCH(OH)CHR2CH(SPh)], can undergo palladium(II)-catalysed cyclization to give 2,3-dihydrofurans, or alkyne... 

Interestingly, silylated propargylic zinc reagents, such as 342, may be better viewed as the allenic zinc reagent 343 which reacts with an aldehyde via a cyclic transition state, affording only the a f/-homopropargylic alcohol 344 with 90% yield (Scheme 91) 22. Alkylzinc halides react only sluggishly with aldehydes or ketones. This reactivity can be... 

A similar synthesis has been described involving partial hydrogenation of the triple bond of a 1-silyl propargyl amine (see Section III.B.l.b). 

Phosphomolybdic acid (PMA) supported on silica gel, CH3CN, rt, 4-7min, 89-95% yield. Esters, benzyl, allyl, silyl, propargyl, and MOM ethers are all compatible with this method. 

Rearrangement intervenes in the hydration of a-silylated propargylic carboxylates. ... 

Table 3.8. Hydromagnesiation of (trimethy silyl)propargyl alcohols with Grignard reagents...

The reaction has also been used to make cyclopentenes by adding silylated propargyl cations to alkenes addition to a titanium imide complex has also been reported. ... 

The retro-1,2-Brook rearrangement was used in a stereocontrolled synthesis of bis-silylated enals and enones (e.g., 152). Deprotonation of propargyl silyl ether 150 led to cr-silylcarbinol 151 via the West rearrangement. The product was best isolated upon cold quench with trifluoroacetic acid. The bis C-silylated propargyl alcohol 151 was the substrate for a stereoselective Lewis acid-catalyzed conversion to enal 152. ... 

Vigreux column gave the silylated propargyl sulfide, b.p. 6S C/18 mmHg, n ... 

Isoxazolines and isoxazoles have been prepared in good yield and excellent purity by reaction of excess nitrile oxide and fluorous labelled silyl ether and silyl propargyl ether respectively [29] (Figure 13). Fluorous variants of the Ugi and Biginelli reaction have also been developed [30]. 

More recently, Inoue and Nakada reported on the first enantioselective Nozaki-Hiyama-Kishi allenylation of terminally silylated propargyl halides using ligands 15a-c (Scheme 12.16). ... 

---