A Route to Carbasugar Analogues - Jonathan Clayden - The ...

Chapter 1: Introduction
Cl
R
+
93
SnBu 3
Pd 2 (dba) 3. CHCl 3 (5%)
PPh 3 (40 mol. %)
acetone, rt
R
94
entry R Time / hr Yield / %
a H 24 80
b 2-Me 32 82
c 3-Me 35 80
d 4-Me 37 76
e 4-Ph 60 71
f 4-i-Pr 34 79
g naphthyl 11 85
61
Table 1.16 – Pd-mediated addition of allyl stannanes
Further inspection of the reaction conditions soon belies the likely oxidative additiontransmetallation-reductive
elimination sequence proposed in Scheme 1.27.
Substitution is presumably seen due to the migration of the Pd II species (95 to 96) to
give π-allyl complex 97 before reductive elimination of tetraene 94. Addition has been
possible to a range of aromatic compounds, although only allylstannane 93 has been
used as the cross coupling partner.
Cl
Pd(0)
94
97
95
L
Pd II L
Cl
Pd II SnBu 3
Bu 3 SnCl
PdII L
Cl
61
93
Scheme 1.27 - proposed catalytic cycle for allylative dearomatisation
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