Exploratory Studies on the Synthesis of Unsymmetrically Substituted Diacetylenes Bearing Trialkoxysilyl Groups and Development of a Method for the Preparation of 1-Lithio-4-(2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3]undecanyl)-1,3-butadiyne:  Synthetic and Mechanistic Aspects

Abstract

CH 3 OCHdCHCtCSi(OCH 3 ) 3 (2), ((Z)-CH 3 OCHdCHCtC) 2 Si(OCH 3 ) 2 (5), and (Z)-CH 3 -OCHdCHCtCSi(OCH(CH 3 ) 2 ) 3 ( 16) have been synthesized from (Z)-CH 3 OCHdCHCtCH (1). Enynes 2 and 16 were subjected to a deprotonation-elimination-deprotonation sequence with 2 equiv of lithium diisopropylamide (LDA) in THF and the expected intermediates (RO) 3 SiCtCCtCLi (R ) CH 3 , CH(CH 3 ) 2 ) allowed to react with R′ 3 SiCl (R′ ) CH 3 , C 6 H 5 ) to produce the unsymmetrical butadiynes (RO) 3 SiCtCCtCSiR′ 3 . Symmetrical butadiynes of the type R′ 3 SiCtCCtCSiR′ 3 were obtained instead of the expected unsymmetrical ones due to cleavage of the C sp -Si(OR) 3 bond by CH 3 OLi formed in situ. Cleavage of the latter bond can be avoided by using a silatrane moiety in place of the trialkoxysilyl group. Thus, (CH 3 ) 3 -SiCtCCtCSi(OCH 2 CH 2 ) 3 N ( 26a) and (C 6 H 5 ) 3 SiCtCCtCSi(OCH 2 CH 2 ) 3 N (26b) were obtained in 61% and 45% yield, respectively, upon subjecting (Z)-CH 3 OCHdCHCtCSi(OCH 2 -CH 2 ) 3 N (20) to a deprotonation-elimination-metalation sequence with 2 equiv of LDA followed by quenching of the intermediate lithium compound LiCtCCtCSi(OCH 2 CH 2 ) 3 N (25) with (CH 3 ) 3 SiCl and (C 6 H 5 ) 3 SiCl. The deprotonation-elimination-metalation sequence applied to 20 is best carried out in pyridine, and the role of pyridine in this reaction is discussed.

Synthesis and X-ray Crystallographic Studies of Diacetylenic Molecules Bearing Triorganosilyl, Triorganostannyl, and Diorganophosphanyl Substituents. Investigation of Their Solid-State and Molten-State Polymerization

“…In the solution 29 Si NMR spectrum, an intense resonance is observed at δ = −28.7 ppm. Since this signal has a chemical shift value close to that of 6b (−28.3 ppm), it is ascribed to Ph 3 SiC⋮C moieties. The 13 C NMR spectrum in CDCl 3 solution exhibits two sets of three signals in the C sp region.…”

“…The first set (δ = 108.0, 107.3, and 106.7 ppm) is assigned to C sp carbons attached to an unsaturated group; the second set (δ = 96.5, 95.1, and 92.9 ppm) corresponds to C sp carbons bonded to silicon. In the region of the spectrum corresponding to aromatic carbons, four new peaks are observed as compared with that of 6b …”

“…Diacetylenes 3 , 3* , 6b , and 6c were elaborated according to the procedure described in Scheme . ,, …”

“…Ph 3 SiC⋮CC⋮CH ( 6b ) was heated to 115 °C for 1 h. The IR spectrum of the resulting solid showed the absence of the ν(C sp −H) and ν C ⋮ C bands of 6b (3310, 2191, and 2038 cm -1 ) . Concomitantly, a new band was observed at 2154 cm -1 that corresponds to the ν C ⋮ C vibration of an enyne skeleton.…”

Silatranes: a review on their synthesis, structure, reactivity and applications

“…The use of a silatranyl moiety however generates a resistance towards nucleophillic attack by CH 3 OLi on the C sp -Si(OCH 2 CH 2 ) 3 N bond. Thus, LiCRCCRCSi(OCH 2 CH 2 ) 3 N can be easily accessed by deprotonation-elimination-metalation of (Z)-CH 3 OCHQCHCRCSi(OCH 2 CH 2 ) 3 N. 66,67 2.1.2 Synthesis of silatranes in the presence of a third reagent by route 1. A general preparative route (Scheme 1b) for the formation of some silatranes involves condensation of tetraalkoxysilane with substituted triethanolamine followed by addition of a third reactant such as a heterocyclic compound (substituents are given in Table 2).…”