[13361-64-3] · C6H12Si · 3-Trimethylsilyl-1-propyne · (MW 112.27)
(propargylation agent; allenylation agent; can give addition reactions on the triple bond)
Alternate Name: propargyltrimethylsilane.
Physical Data: bp 91-93 °C/760 mmHg; 40 °C/140 mmHg; d 0.753 g cm-3; n
Solubility: sol ether, THF, CH2Cl2.
Form Supplied in: colorless liquid, commercially available.
Analysis of Reagent Purity: IR and NMR.
Purification: by distillation.
Handling, Storage, and Precautions: usually stored in a refrigerator. The reagent should be handled in a well-ventilated hood.
3-Trimethylsilyl-1-propyne is the simplest of the propargylic silanes, which are convenient reagents in organic synthesis.5,6
3-Trimethylsilyl-1-propyne is metalated easily by using an organomagnesium or a lithium compound, leading to the corresponding alkynic organometallic reagent which can react with many electrophiles.
These reactions may be obtained with various halides, a number of them having other functionalities (eqs 2 and 3).
These reactions allow preparation of b-alkynic alcohols (eq 4); the use of n-Butyllithium, followed by Diethylaluminum Chloride, may increase the yield.
These are exemplified by eqs 5 and 6. Under the conditions of eq 6, the major product results from further reaction between the initial alcoholate and the excess Formaldehyde. Secondary and tertiary alcohols are also obtained easily (eq 7). The yields are best when n-BuLi is used as the base and when HMPA is used as a cosolvent in the reaction with the ketone.
These are exemplified by eq 8.
These are exemplified by eq 9.
The propargyltrimethylsilanes undergo Lewis acid-catalyzed reactions with electrophiles, with regiospecific rearrangement, to give substituted allenes eq (10)18-21. The catalysts usually employed are Aluminum Chloride, Boron Trifluoride Etherate, and Titanium(IV) Chloride.
Few examples have been described. Generally, the reaction occurs with regiospecific rearrangement. Substitution of halides18 is shown in eq 11, and of OH, OSiMe3, and OCOR groups19,20 in eq 12.
Ortho-propynyliodoarenes are obtained by reductive iodono-Claisen rearrangement of allenyliodinanes (eq 13).21 When both ortho positions and the para position of aryliodinanes are occupied, ipso-propynylarenes are formed (eq 14).
These are exemplified by eqs 15 and 16. The synthesis of C-glycosides bearing an allenyl group has been accomplished25,26 by use of 3-trimethylsilyl-1-propyne.
These reactions generally lead to a-allenyl alcohols (eq 17). With titanium(IV) chloride as catalyst, the major product is a chloroprenic derivative formed from the a-allenyl O-silylated alcohol (eq 18).22 The yields are good with aliphatic aldehydes bearing a primary or a secondary group and with activated ketones; they are poorer with aliphatic ketones (23-25%). With two equivalents of an aldehyde, the formation of a heterocyclic compound may be observed (eq 19).28 By using Tetra-n-butylammonium Fluoride as catalyst, a-allenyl alcohols are easily obtained29 with aliphatic and aromatic aldehydes (eq 20).
These reactions allow the preparation of a-allenyl amines and amides (eqs 21 and 22). The photoinduced addition reaction leads to a mixture of two products (eq 23).32
These reactions lead to a-allenyl ketones (eq 24).
3-Trimethylsilyl-1-propyne seems unable to undergo 1,4-addition to monofunctional conjugated carbonyl derivatives such as R´CH=CH-CO-R´´, R´CH=CH-CO2R´´, or R´CH=CH-CN, but readily undergoes 1,4-addition reactions with alkylidenemalonates and analogs (eq 25)3a and with conjugated acyl cyanides (eq 26).34 Similar results are obtained with alkylideneacetylacetates and -cyanoacetates (45-65%).3a
3-Trimethylsilyl-1-propyne reacts with Octacarbonyldicobalt to give the complex shown in eq 27.35 This complex can react with alkenes to lead to 2-trimethylsilylmethylcyclopentenones (28-30%).
This is shown in eq 28.
University of Poitiers, France