Ph. D. THESIS 2009

Sch e m e 1 . Th e co n ve r sio n o f 1 in t o 2 via h y d r o ly sisd
e ca r b o xy la tio n r o u t e .
The reaction underwent with the complete hydrolysis and decarboxylation
of all four ester groups. The total transformation is supported by TLC
chromatography as well as by the melting point of the crude product, which is
0.5°C smaller than that of the pure compound 2.We have to highlight the
novelty of this method through its simplicity (one-step), high efficiency (yields
over 96%) and because it requires no catalyst.
We also developed an alternative way to the above proposed method. Thus,
compound 1 was deposited on a solid support, placed into a teflon sealed tube
and irradiated in microwave field.
The results of these two methods can be summarized in Table 1:
Table 1 Comparisson between classic and microwave irradiation methods
Method Yield (%) M.p.
7
(ºC)
classic Method (a) 98 250
microwave
irrad.
Method (b) 90 249-250
The advantages of these syntheses over the previous ones lie in the
direct transformation of 1 into 2, as well as in the significantly increased yields,
due to the absence of the acidic conditions and to the facile work-up procedure.
1.3. Structural aspects in solution
The bicyclic tetraester 1 and the bicyclic diketone 2 were both investigated
by NMR spectroscopy in solution at room temperature in order to establish
their structure and thereby to evidence the complete hydrolysis-decarboxylation
of the precursor 1. This may present as most of β-ketoesters two tautomeric
forms, enol and ketone, in equilibrium.
Keto-enol tautomerization of compound 1 (Scheme 2) in CDCl3 solution
has been investigated by NMR spectroscopy.