Page 139 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements
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4.8 CARBENE AND ALKENE ANALOGS 119
The reactions can be broadly classified into two categories. The products shown in green
arise via a cycloaddition reaction; the others form by oxidative addition. Note that the steric
protection afforded by the trimethylsilyl group even allows the formation of a trisilaallene
(the product at the bottom).
REVIEW PROBLEM 4.15*
Assume that the oxidative additions (shown in black) and the cycloadditions (shown
in green) depicted above (reaction set 4.52) are concerted one-step processes. Use
arrow pushing to rationalize one reaction from each of the two categories.
REVIEW PROBLEM 4.16*
Protchenko et al. have reacted a sterically hindered boryllithium (see Section 3.6
for a reminder) with a sterically hindered (amino)tribromosilane to produce a ther-
mally stable (amino)borylsilylene, as shown below (Angew. Chem. Int. Ed. 2013, 52,
568–571):
Dipp
N
B Li(THF) 2
N (2 equiv)
Dipp
Dipp
Dipp Br Me Si N
C D , 20 °C 3
6 6
N Si Si
Dipp
Br Dipp
Me 3 Si Br B
N N
N Dipp
− B Br, − 2 LiBr
N
Dipp
Me Me
Dipp =
Me Me
Suggest a mechanism for the reaction. Can you think of a rationale behind the
researchers’ choice of amino and boryl substituents for the silylene?
