Silenes synthesis

Mori M (2005) Synthesis and Reactivity of Zirconium-Silene Complexes. 10 41-62... 

Generalized silene structure Method of synthesis Common substituents Reference... 

It may well be that activity in the area of silene chemistry has peaked. Certainly, the number of papers currently published is lower than it was a few years ago. This may be due, at least in part, to the fact that many of the easier and more obvious experiments have been attempted. However, only the discovery of important applications is required for the field to be revitalized. In particular, the successful synthesis of useful polymers... 

After decades of unsuccessful attempted syntheses, Gusel nikov and Flowers in 1967 reported the first compelling evidence for the existence of silenes, compounds containing a double bond between silicon and carbon. This initiated a renewed interest in the synthesis and behavior of stable silenes,8 disilenes,b iminosilanes,c phosphasilenesd and their heavier homologs. 

Summary The formation, reactivity, and cycloaddition behavior of neopentylsilenes towards suitable reaction partners is described. Especially l,l-dichloro-2-neopentylsilene. Cl2Si=CHCH2Bu (2) - easily obtained from vinyltrichlorosilane and LiBu - is a useful building block for the synthesis of SiC four membered ring compounds. These can be converted into the isomeric Diels-Alder and retro ene products upon thermolysis reactions. The mode of the silenes cycloaddition reactions ([4+2] vs [2+2] addition) can be directed by either the substitution pattern at the Si=C moiety, the choice of reaction partners or the conditions. Furthermore the products resulting from cycloaddition reactions open up a wide variety of following reactions, which possibly will lead to new organosilicon materials or pharmaceutical compounds. 

In summary, it is clear that in the relatively few years since the synthesis of the first silene was reported, a wide variety of reliable routes has been developed which can lead cleanly to silenes that vary widely in structure and stability. 

Intramolecularly coordinated silenes have been prepared by Oehme et al.868-871 Adopting their general procedure for the synthesis of silenes (Scheme 33), 8-dimethylaminonaphth-l-yl lithium has been reacted with (Me3Si)3SiCHCl2 yielding the disilene (Me3Si)RSiC(SiMe3)2 929 via the intermediates 930-933 (R = 8-dimethyl-aminonaphth-l-yl) (Scheme 131). 

Mori M (2005) Synthesis and Reactivity of Zirconium-Silene Complexes. 10 41-62 Moriuchi T, Hirao T (2006) Ferrocene-Peptide Bioconjugates. 17 143-175 Morokuma K, see Musaev G (2005) 12 1-30... 

The attempted synthesis of 104 from its LiF adduct by salt elimination leads exclusively to the silene 104a65,66. 104a can be reacted with benzophenone to give the [2 + 4] and [2 + 2] cycloadducts 105 and 10667. The [2 + 4] cycloadduct of silene 104 cannot be obtained directly. The adducts 105 and 106, however, rearrange to the thermodynamically more stable 107, probably via the donor adducts 108, 109 and the free silenes 104 and 104a (equation 24). 

The most straightforward synthesis of unsaturated Si=C compounds is the formation of the double bond by 1,2-elimination of a salt. This method has been widely used by N. Wiberg s and N. Auner s groups in recent years to produce a variety of different silenes. 

The 1,3-silyl shift in aryl disilanes is suppressed when the aromatic ring is ortho-substituted144. An attempted silylene synthesis from 1,3-dimesitylhexamethyltrisilane 259, however, led to low yields of silylene trapping products (ca 30% generation of Me2S ). The major pathway is the homolytic cleavage of the trisilane, followed by disproportionation of the radicals 260 and 261 to the silene 262 and the disilane 263 (equation 65). 

A photochemical approach via a silylene-to-silene rearrangement was followed by Fink and coworkers in their synthesis of silacyclobutadienes in a 3-methylpentane matrix at low temperatures161. Irradiation of the cyclopropenyltrisilane 294 gives the relatively stable cyclopropenylsilylene 295. 295 can be efficiently converted to silacyclobutadiene 296 by irradiation into the visible absorption band of the silylene (equation 72)161 162. 

The synthesis of siladihydrotriazoles 412a is easily achieved by the [2+3] cycloaddition reaction of azides RN3 with the silenes Me2Si=C(SiMe3)2 92 (equation 226). 

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