"Front Matter". In: Organosilanes in Radical Chemistry - Index of

164 Consecutive Radical Reactions
Another strategy for the synthesis of N-containing heterocycles utilizes the
azido group as the radical acceptor (Reaction 7.50). This is possible by using
(TMS) 3SiH which is relatively inert towards azides and can activate alkyl
bromides or thionocarbonates as radical precursors [60,61]. An example is
given in Reaction (7.51) where the amine product was tosylated before workup.
Alternatively, the carbon-centred radical derived by the addition of
(TMS) 3Si: radical to the carbonyl group of 44 cyclized to the azido group to
afford the bicyclic product in good yields, independently from the ring size
(Reaction 7.52).
N
N
N N
N N − N N
2
O
S
OMe
O
C
OPh
N 3
1. (TMS) 3 SiH
AIBN, 80 �C
2. TsCl, py
O
OMe
N
H Ts
60%
O N3 N
n
CO2Et (TMS) 3SiH
AIBN, 80 �C
n
CO2Et 44, n = 1, 2
78%
(7.50)
(7.51)
(7.52)
The a-silyloxy alkyl radical generated by the addition of (TMS) 3Si: radical
to the aldehyde moiety of 45 has been employed in radical cyclization of
b-aminoacrylates (Reaction 7.53); the trans-hydroxy ester and the lactone in a
2.4:1 ratio were the two products [62].
H
O
CO2Et N
CO2Me (TMS) 3SiH
AIBN, 80 �C
OH
CO2Et N
CO2Me +
O
N
CO 2Me
45 60% 25%
O
(7.53)
Analogously to the carbocycle and oxycycle synthesis, cyclic amines can
be obtained by the hydrosilylation of a suitable enyne, such as 46 (Reaction
7.54), which gave the six-membered ring via a 6-endo cyclization of the vinyl
radical onto the C N bond [63]. In another example, the isothiocyanide
w
functionality of compounds 47 or 48 reacts with silane under radical conditions