Trimethyl(triphenylmethoxy)silane

In the title molecule, C22H24OSi, the Si—O—C angle is 139.79 (11)°, the O—C—C angles of the triphenylmethoxy group are in the range 106.13 (13)–109.22 (14)° and the O—Si—C angles of the trimethylsilyloxy group are in the range 103.08 (10)–113.53 (10)°. In the crystal, face-to-face π–π interactions are observed between the phenyl rings [centroid separation = 4.194 (1) Å, interplanar spacing = 3.474 Å and centroid shift = 2.35 Å]. The three phenyl groups of the triphenylmethyl substituent are mutually nearly perpendicular, with dihedral angles in the range 80.49 (8)–81.53 (8)°. There are only weak intermolecular van der Waals interactions in the crystal.

In the title molecule, C 22 H 24 OSi, the Si-O-C angle is 139.79 (11) , the O-C-C angles of the triphenylmethoxy group are in the range 106.13 (13)-109. 22 (14) and the O-Si-C angles of the trimethylsilyloxy group are in the range 103.08 (10)-113.53 (10) . In the crystal, face-to-faceinteractions are observed between the phenyl rings [centroid separation = 4.194 (1) Å , interplanar spacing = 3.474 Å and centroid shift = 2.35 Å ]. The three phenyl groups of the triphenylmethyl substituent are mutually nearly perpendicular, with dihedral angles in the range 80.49 (8)-81.53 (8) . There are only weak intermolecular van der Waals interactions in the crystal.

Comment
Trimethylsilylation of hydroxyl group in organic compounds finds immense applications in preparative organic chemistry (Kocienski, 1994;Greene & Wuts, 1999). Trimethylsilyl is regarded as one of the most popular and widely used groups for protecting hydroxyl function in several chemical conversions and multi-step organic syntheses of poly-functional compounds. Silylethers are also valuable synthetic monomers for the production of organosilane polymers and materials. Several methods were reported for the trimethylsilylation of alcohols and phenols using a variety of silylating agents in the presence of catalysts however most of the reported methods of trimethylsilylation do not work well to furnish 2,2-dimethyl-2-triphenylmethoxy-2-silaethane from triphenylmethanol. Under this purview, we have been motivated to develop an efficient method for the synthesis of the title compound from triphenylmethanol. In continuation of our efforts to develop useful synthetic methodologies for organic transformations, we herein wish to report a newly developed synthetic protocol and crystal structure of 2,2-dimethyl-2-triphenylmethoxy-2-silaethane.
The Si-O bond length is 1.6379 (14) Å and Si-O-C bond angle is 139.79 (11)°. Owing to the absence of any strong donor group, cohesion of the crystal is mainly achieved by van der Waals interactions (Fig.2). The closest contact of 3.611 (4) Å occurs between atoms C8 and C10 (-x + 2, -y + 2, -z).

Experimental
The synthesis of the title compound was carried out following a newly developed methodology. An oven-dried screw cap test tube was charged with a magnetic stir bar, dehydrated copper chloride (0.0067 g, 0.05 mmol), triphenylmethanol (0.26 g, 1 mmol) and trimethylsilyl cyanide (TMSCN, 0.198 g, 2 mmol). The tube was then evacuated and back-filled with nitrogen.
The tube was placed in a preheated oil bath at 170°C and the reaction mixture was stirred vigorously for 1 h. The progress of the reaction was monitored by TLC, and on completion the reaction mixture was cooled to room temperature. Dried ethyl acetate (10 ml) was added and shaken well; copper chloride was removed by filtration. The filtrate was concentrated under reduced pressure and the residue was purified via column chromatography using silica gel (60-120 mesh) and petroleum ether(PE)-ethyl acetate (EtOAc) (98:2) mixture as eluent. The recrystallization of the solid product from PE/EtOAc afforded the title compound (302 mg, yield 91%) with the m.p. 323-325 K.

Refinement
All H atoms were positioned geometrically and were treated as riding on their parent C atoms, with C-H distances of 0.93-0.96 Å; and with U iso (H) = 1.2U eq (C), except for the methyl groups where U iso (H) = 1.5U eq (C).