1-Trimethylsilyl-1-alkynes deprotection

Ethynylaniline. See the general procedure for the deprotection of trimethylsilyl alkynes. The compounds used were 4-... 

Deprotection of N-2 by ozonolysis furnishes triazoles 1225 (Scheme 202) <2003JA7786>. Finding that 1,3-dipolar cycloaddition of alkynes 1222 to trimethylsilyl azide, carried out in DMF/MeOH in the presence of Cul as a catalyst, leads directly to products 1225 with much higher yields provides a significant progress to the synthesis of N-unsubstituted 1,2,3-triazoles <2004EJO3789>. 

All the reagents listed can be used to cleave trimethylsilyl groups from acetylenes fluoride, potassium carbonate under basic conditions in methanol, or silver nitrate/potassium cyanide.9 With the third method advantage can be taken of the fact that the later transition metals (e.g., copper or silvei) complex readily with acety-lides. Workup with concentrated potassium cyanide solution causes compound 32 to be cleaved tu alkyne 33. In this way silylated a -kynes can be deprotected in the presence of 0-silyl groups. 

Perhaps the most widely reported use of silver acetylides is in the deprotection of 1-trimethylsilyl-l-alkynes. Schmidt and Arens first reported the treatment of 1-trimethylsilyl-l-alkynes with silver nitrate to give the silver acetylide in situ, which, when treated with potassium cyanide, is converted to the free alkyne (Scheme 1.63).137 This very mild and selective, but toxic, means for the selective... 

Two remarkable intramolecular reorganizations of the Diels-Alder adducts of methyl 2-chloro-2-cyclopropylideneacetate (1-Me) onto furans should be mentioned here. In a reaction of 1-Me with 2,5-bis(trimethylsilyl)furan (263) the unstable adduct 264 underwent a spontaneous deprotection followed by ring opening to give the dioxospiro[2.5]octene derivative 265 (Scheme 76) [7 m]. The Pauson-Khand reaction of the transformed Diels-Alder adducts 70, 71 of 1-Me have been discussed above (Scheme 18), however, when the compounds endo,-exo-62 e were treated under Pauson-Khand conditions, but at higher temperature, the interesting Co2(CO)8-promoted stereoselective rearrangement, in the presence as well as in the absence of an alkyne component, has been observed. The cis- and frans-substituted 6-methylenespiro[2.4]hexanes 266 were isolated as main products in these reactions (Scheme 76) [19b]. 

Triazole derivatives could be synthesized from different starting substrates. Various triazoles 155 were synthesized from nonactivated terminal alkynes 152, allyl methyl carbonate 153 and trimethylsilyl azide 154 in a [3 + 2] cycloaddition with the use of the Pd(0)-Cu(I) bimetallic catalyst <03JA7786>. The allyl group of 155 was efficiently deprotected by ruthenium-catalyzed isomerization followed by ozonolysis to give 4-substituted triazoles 156. a-Aminoacetophenones 157 were reacted with hydrazines in acetic acid to give an efficient... 

This reaction has been modified to use a mixture of CU2CI2/CUCI2 in pyridine for the coupling. In addition, terminal alkynes protected by trimethylsilyl group can also couple under this reaction conditions via prior deprotection by K2C03. ... 

In order for the 2-(trimethylsilyl)ethylthio unit to lose its protecting group upon treatment with the fluoride, the sulfur must be attached to an unsaturated carbon. Hence the fluoride mediated sulfur deprotection is feasible for 2-(trimethyl-silyl)ethylthio substituted (het)arenes, alkenes, alkynes, and acid derivatives such as carboxylic and selenothiophosphinic acid salts. In thiolate form, the substrates have value for the formation of self-assembled monolayers or as metal complexing agents. Simple addition of acid to the thiolate to give a stable thiol characterizes 2-(trimethylsilyl)ethanethiol as a simple M" (HS) equivalent that is only capable of a single substitution reaction. ... 

Ethynyl-2-(ethynylphenyl)-4-nitroaniIine. See the general procedure for the deprotection of trimethylsilyl-protected alkynes. 74 (0.10 g, 0.27 mmol) was deprotected to the terminal alkyne and the free amine using the procedure described above using K2CO3 (0.19 g, 1.35 mmol), MeOH (15 mL), and CH2CI2 (15 mL). The reaction mixture was allowed to stir at room temperature for 2 h. The resultant mixture was subjected to an aqueous workup as described above. Due to the instability of conjugated terminal alkynes, the material was immediately used in the next step without additional purification or identification. 

Methyl 4-ethynyIbenzoate (89). See the general procedure for the deprotection of trimethylsilyl-protected alkynes. The compounds used were methyl 4-(trimethylsilylethynyl)benzoate (0.75 g, 3.23 mmol), K2CO3 (2.23 g, 16.15 mmol), MeOH (50 mL) and CH2CI2 (50 mL) for 2 h. Extraction of the product afforded 0.49 g of the desired product that was immediately reacted in the next step. 

General Procedure for the Deprotection of Trimethylsilyl-Protected Alkynes. To a round bottom flask equipped with a stir bar were added the protected alkyne, K2CO3 (5 equiv per protected alkyne), MeOH, and CH2CI2. The reaction was heated, and upon completion the reaction mixture was diluted with CH2CI2 and washed with brine (3x). The organic layer was dried over MgS04, and the solvent removed in vacuo. 

The first example of the use of CuAAC reaction in this context was the preparation of a diblock copolymer Opsteen and van Hest used a trimethylsilyl blocked ATRP initiator (6) to initiate the CRP of styrene and methyl methacrylate (MM A), which after deprotection yielded a polymer chain with an alkyne unit at one end and a bromide at the other (Scheme 7.18) [34]. Similarly, using a simple a-bromo ethylbenzene as the ATRP initiator, polystyrene with a benzylic bromide at one end is readily synthesized quantitative transformation of this bromide to an azide was achieved by treatment with a httle excess of trimethylsilyl azide in the presence of tetrabutylammonium fluoride (TBAF). 

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