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

56 Reducing Agents
R
Br
R
O R O
O
N
O
R = H or Me
Br Br
(TMS) 3 SiH
AIBN, 75 �C
R
(TMS) 3SiH
hν(254nm), r.t.
99%
O
99%
N
O
(4.10)
(4.11)
A highly diastereoselective and efficient method for the synthesis of (2 0 S)- and
(2 0 R)-2 0 -deoxy[2 0 - 2 H]ribonucleoside derivatives starting from the corresponding
bromide at the 2 0 position has been developed [34]. Reactions (4.12) and (4.13)
show the flexibility of this methodology to obtain a single diastereoisomer, (2 0 S)
and (2 0 R), respectively. The high stereoselectivity in these reactions is due to the
transfer of hydrogen or deuterium atoms from the less hindered side of the ring.
It is worth mentioning that the solvent employed in Reaction (4.13) was either
THF-d8 or 2,2,5,5,-tetramethyl-THF, in order to eliminate a small percentage of
hydrogen donation from the reaction medium.
RO
RO
O
D
O
N
RO Br
O
H
O
N
RO Br
NH
NH
O
(TMS) 3 SiH
Et 3B, THF, −78 �C
R,R = −Si(i-Pr) 2OSi(i-Pr) 2 −
O
(TMS) 3 SiD
Et 3B, THF-d 8, −78 �C
R,R = –Si(i-Pr) 2OSi(i-Pr) 2 –
RO
RO
O
D
O
N
NH
RO H
(2'S) 88%
RO
O
H
D
O
N
O
NH
(2'R) 89%
O
(4.12)
(4.13)