A Convenient One-Pot Synthesis of 1,4-Dihalobutadienes from Alkynes via Titanacyclopentadienes and Their Transformation to a Series of Silole Derivatives

Synthesis of Siloles (and Germoles) that Exhibit the AIE Effect

“…The reaction of 1,4-diphenyl-1,3-butadiyne with Ph 2 SiH 2 provided $50% yields of 1,1,2,5-tetraphenylsilole but gave virtually no silole product when Et 2 SiH 2 or PhMeSiH 2 was utilized. Specific formation of the same 1,1,2,5-tetraphenylsilole was reported previously from the Tamao procedure that started with phenylacetylene and TiðO i PrÞ 4 = i PrMgCl to provide the 1,4-diiodo-1,4-butadiene that was lithiated and converted to the silole (21% yield) through reaction with Si(OMe) 4 [58]. Another route to 1,1-dimethyl-2,5-diarylsiloles involved the reaction of 1,3-diynes first with Li 2 Te to give the tellurophene, which could be ring opened with t BuLi and treated with Me 2 SiCl 2 to give the silole (Ar ¼ Ph, 59%; four other examples) [62b].…”

“…Halogenation provides the 1,4-diiodo-1,4-butadiene (10 examples) or dibromo analog (three examples). Conversion to the dilithio-1,4-butadiene and quenching with Si(OMe) 4 provided the silole 2,5-R 2 -3,4-R 0 2 C 4 SiðOMeÞ 2 (21-52%) [58].…”

“…This side reaction can be suppressed by utilizing relatively 'bulky' exocyclic substituents at silicon, particularly 1,1-ð i PrÞ 2 siloles at low temperature, but the yields are still modest. An alternative route involves generating the zirconacycle from Me 3 SiC À À À À À À CMe and Cp 2 ZrCl 2 = n BuLi in situ followed by treatment with I 2 [64b] or through a comparable titanacycle [58] and cleavage with PyHBr 3 , I 2 or ICl. The use of ICl/AgBF 4 gave useful yields even when 1,1-substituents were Me or Et.…”

Synthesis and Structure-Property Relationships of Phosphole-Based π Systems and Their Applications in Organic Solar Cells

“…Titanacycle-mediated syntheses of 2,5-disubstituted heteroles have been independently reported by several groups. [14][15][16] The success in isolating 1 led me to investigate the chemistry of π-conjugated phosphole materials, which is described in the next section.…”

The Divalent Titanium Complex Ti(O-i-Pr)4/2i-PrMgX as an Efficient and Practical Reagent for Fine Chemical Synthesis

“…The intermolecular coupling reactions mediated by Ti(O-i-Pr) 4 /2 i-PrMgX, however, frequently show excellent regioselectivity which includes the homocoupling of acetylenes or allenes, coupling between internal acetylenes and terminal acetylenes, and cross-coupling of allenes and acetylenes. Representative results are summarized in Equations 44, [77,96] 45, [97] 46, [98] and 47, [96,97] respectively. Among these, the regioselective cross-coupling reaction between internal and terminal acetylenes exemplified in Equation 46 is especially noteworthy because it affords a highly practical method for synthesizing a variety of conjugated dienes, including those having a functional group, which are frequently found as a partial structure of naturally occurring products and are also useful intermediates in organic synthesis.…”