4-Trimethylsilyl-3-butyn

Somei adapted this chemistry to syntheses of (+)-norchanoclavine-I, ( )-chanoclavine-I, ( )-isochanoclavine-I, ( )-agroclavine, and related indoles [243-245, 248]. Extension of this Heck reaction to 7-iodoindoline and 2-methyl-3-buten-2-ol led to a synthesis of the alkaloid annonidine A [247]. In contrast to the uneventful Heck chemistry of allylic alcohols with 4-haloindoles, reaction of thallated indole 186 with 2-methyl-4-trimethylsilyl-3-butyn-2-ol affords an unusual l-oxa-2-sila-3-cyclopentene indole product [249]. Hegedus was also an early pioneer in exploring Heck reactions of haloindoles [250-252], Thus, reaction of 4-bromo-l-(4-toluenesulfonyl)indole (11) under Heck conditions affords 4-substituted indoles 222 [250], Murakami described the same reaction with ethyl acrylate [83], and 2-iodo-5-(and 7-) azaindoles undergo a Heck reaction with methyl acrylate [19]. 

With telluronium salt (d) (typical procedure) A solntxon of n-BuLi (1.5 mmol) in hexane is added to a solution of the telluronium salt (0.65 g, 1.5 mmol) in dry THF (10 mL) at -78°C under N2. After 30 min, a solution of p-chlorobenzaldehyde (0.168 g, 1.2 mmol) in THF (2 mL) is added dropwise at -78°C and the reaction mixture is allowed to warm at room temperature. After the reaction is complete (monitored by TLC), H2O (1 mL) is added and the solution is stirred for another 1 h. The mixture is then extracted with ether (3x5 mL). The combined extracts are washed with brine, dried (Na2S04), filtered and concentrated under vacuum. Flash chromatography on an SiOj column gives l-(p-chlorophenyl)-4-(trimethylsilyl)-3-butyn-l-ol (0.265 g (87%) (98% GC purity)). 

Enzymatic reduction of 23a with recLBADH and CPCR resulted in unsatisfactory results (60% and 49% ee) as well. The results mentioned above indicate that a bulky substituent at the alkyne moiety results in a higher selectivity of the reduction. Furthermore, Bradshaw et al. reported that Lactobacillus kefir ADH, an enzyme highly homologous to LB ADH, affords (R)-4-trimethylsilyl-3-butyn-2-ol [(R)-25j with an ee of 94% in 25% yield [39bj. In our investigations ketone 23b was reduced by recLBADH with almost quantitative conversion. The enantiomeric excess and absolute configuration of the product were determined by desi-lylation with borax converting alcohol (R)-25 into enantiopure (R)-3-butyn-2-ol [(R)-24j (Scheme 2.2.7.14). 

Trimethylsilyl)-3-butyn-l-ol Tetrahydropyranyl Ether, and (Z)-4-(Trlmethylsilyl)-3-buten-l-ol... 

The combined organic phases are washed with two 200-mL portions of water, four 200-mL portions of saturated sodium bicarbonate solution, and two 200-mL portions of saturated sodium chloride. The organic phase is dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure at room temperature using a rotary evaporator. The crude product is distilled through a short-path distillation apparatus under reduced pressure to give 45.2 g (0.318 mol, 71% yield) of 4-(trimethylsilyl)-3-butyn-l-ol, bp 78-79°C (10 mm), as a colorless liquid (Notes 4 and 5). 

The submitters report that Z-4-(trimethylsilyl)-3-buten-l-ol of >98% isomeric purity can be obtained in ca. 60% overall yield by a more lengthy sequence involving hydroalumination-protonolysis of the tetrahydropyranyl (THP) ether of 4-(trimethylsilyl)-3-butyn-l-ol followed by cleavage5 of the THP ether with pyrldinium p-toluenesulfonate in methanol. This sequence is less convenient for the tetrahydropyridine synthesis described In the next procedure, since the Isomeric purity of the vlnylsilane is not Important for the cycllzatlon reaction.6... 

Silylated acetylenes can also be acylated bis(trimethylsilyl)acetylene reacts with acetyl chloride in the presence of aluminum chloride in carbon disulfide, giving 4-(trimethylsilyl)-3-butyn-2-one in 90% yield 493... 

In a similar manner, allenylborane derived from 3-(tert-butyldimethylsilyl)-l-(trimethylsilyl)-propyne gives mainly (lS,2i )-2-(fert-butyldimethylsilyl)-l-[2-(3-methyl-3-buten-l-ynyl)-l-cyclopentenyl]-4-(trimethylsilyl)-3-butyn-l-ol (54%) and (lS,2i )-2-(ferf-butyldimethylsilyl)-l-[2-l-cyclohexenylethynyl)-l-cyclopentenyl]-4-(trimethyl silyl)-3-butyn-l-ol (55%) (Chart 6.17) [1]. 

Article previously published in the electronic Encyclopedia of Reagents for Oigenic Synthesis as 4-Trimethylsilyl-3-butyn-2-ol. DOI 10.1002/ 047084289X. m01324. 

In the presence of CO, the Pd(PhCN)2Cl2-catalyzed cyclization of 1,1-disubstituted 4-(trimethylsilyl)-3-butyn-l-ols produces y-butyrolactones (eqs 73 and 74).4 ... 

KINETIC RESOLUTION OF A SECONDARY ALCOHOL (4-TRIMETHYLSILYL-3-BUTYN-2-0L) BY LIPASE-CATALYZED ACETYLATION WITH VINYL ACETATE... 

J.A. Marshall, H. Chobanian, Lipase-catalyzed resolution of 4-trimethylsilyl-3-butyn-2-ol and conversion of the (R)-enantiomer to (R)-3-butyn-2-yl mesylate and (P)-l-tributylstannyl-l, 2-butadiene, Org. Synth. 82 (2005) 45-54. 

---