LETTER
C-Quaternary Vinylglycinols
2851
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palladation step or a concurrent pathway via intermediate
A remains to be determined (Scheme 2).
In order to demonstrate the utility of the cyclization reac-
tions, several 4-substituted 4-vinyloxazolines 3a–c were
transformed to N-Boc vinylglycinol derivatives 5a–c by a
one–pot, two-step procedure that involved hydrolysis and
subsequent protection (Scheme 3).
R
OH
R
1. 6 M HCl (aq), EtOH, r.t.
O
O
(7) [2,3]-Sigmatropic rearrangement of selenimides:
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N
2. Boc2O, sat. NaHCO3 (aq)
THF, r.t.
HN
CCl3
Ot-Bu
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5a, 70%
5b, 79%
5c, 66%
3a, R = Me
3b, R = Ph
3c, R = 4-MeOC6H4
Lett. 1994, 35, 8743.
Scheme 3 Transformation of vinyloxazolines 3a–c to the corre-
sponding N-Boc vinylglycinols 5a–c
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In summary, we have developed a short and high-yielding
procedure for the synthesis of C-quaternary vinylglycin-
ols starting from 2-substituted 1,4-butenediols. Our cur-
rent attempts are devoted to develop an asymmetric
version of bisimidate cyclization.
Supporting Information for this article is available online
tains descriptions of the synthesis and characterization of diols 1
and bisimidates 2, general procedures for the cyclization of bisimi-
dates 2, characterization of the cyclization products 3 and 4, de-
scriptions for the transformation of oxazolines 3 to N-Boc-protected
1
vinylglycinols 5, and copies of H NMR and 13C NMR spectra of
compounds 2–5.
Acknowledgment
Financial support from ERAF 2010/2DP/2.1.1.1.0./10/APIA/
VIAA/074 is gratefully acknowledged.
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