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Scheme 4.26 Design of novel acyl-fulvenes.
BzN
O
MeO 2C Bn
145e
•
Rh(I)
BzN
MeO2C Bn
O
285
O
MeLi
BzN
MeO2C Bn
Subjecting 145e to 10 mol% of [Rh(CO)2Cl]2 under CO atmosphere led to formation of the
cross-conjugated triene 146e, which was isolated in 70 % yield (Scheme 4.27). To circumvent
the formation of triene, the newly developed cationic Rh(I)-conditions were applied next.
Treatment of 145e to the in situ prepared catalyst (10 mol% [Rh(CO)2Cl]2, 30 mol% PPh3 and 22
mol% AgBF4) at 50 °C resulted in complete consumption of the starting material in 3h and
generation of a mixture of unidentified products in 44% yield by mass recovery. The major
compound isolated from this mixture in 22% yield displayed a molecular ion peak in the mass
spectrum same as the starting material (m/z = 401), indicating that it is likely a product of an
isomerization reaction. Unfortunately, the desired cyclocarbonylation product 285 was not
observed.
Scheme 4.27 Attempted cyclocarbonylation reactions of 145e.
BzN
O
MeO 2C Bn
BzN
O
MeO 2C Bn
145e
•
•
145e
10 mol% [Rh(CO) 2Cl] 2
DCE, CO (1 atm), rt
10 mol% [Rh(CO) 2Cl] 2
30 mol% PPh 3, 22 mol% AgBF 4
DCE, CO (1 atm), 50 o C, 3h
BzN
MeO2C Bn
O
146e 70%
mixture of unidentified products
44% by mass recovery
O
286
BzN
MeO2C Bn
O
O
285 not observed
BzN
MeO2C Bn
O
O
285 not observed
Due to these discouraging results, further study on generating a library of amino-acid derived
fulvenes was discontinued. In addition to stabilizing the fulvene moiety by installing an acyl
substituent, another potential strategy for future investigation involves exploiting the reactivity of
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