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

1.4 – Metal complexation
Ph
O
O
N
O
i) LDA
ii)
O
Mn(CO) 3
+
Ph
O
O
O
N
H
O
Mn(CO) 3
d.r. = 3.5:1
O
i) LiAlH 4
ii) p-nitrobenzoyl chloride
iii) Recrystallisation O 2 N
O
H
i) NOPF 6
ii) NaBH 4
>97:3 dr
Mn(CO) 3
O
O
O 2 N
O
H
O
H
Mn(CO) 3
O
COOCH 3
(+)-Juvabione
58
Scheme 1.26 – asymmetric synthesis using Mn(CO) 3 methodology
The (η 2 -arene) Os(NH 3 ) 2+ 5 complexes are also susceptible to dearomatisation, and this
chemistry has recently been reviewed. 60 However the toxic nature of the reagent, and
limited use in asymmetric functionalisation of benzenoid rings means it will not be
discussed.
1.4.3 Pd-mediated dearomatisation
The attempted synthesis of homoallyl benzene by the cross-coupling of benzylchloride
and tributylallylstannane (93), yielded tetraene 94 the apparent product of 1,4-addition
(Table 1.16).
48