Scheme 1. Reagents and conditions: (i) MeLi in Et₂O–THF, 1 h at −78 °C, 20% aq NH₄Cl quench (cf. Ref. 10); (ii) Ac₂O/Et₃N + 20 mol % DMAP, 20 h at rt; (iii) LDA in THF–hexanes at −78 °C, then TBSCl followed by 1 equiv HMPA at −78 °C, then rt for 12 h.

Scheme 2. 

Scheme 3. 

Table 1.

Functionalisation at C–H centres using the O-oxiranylcarbinyl O-tert-butyldimethylsilyl ketene acetal 4

^a Generally 1mmol of acetal 4; the total reaction time was usually 2.5h. A=benzene solvent, bath temp 70°C; TBHN (0.05equiv) added initially and again after 20 and 40min; B=refluxing benzene solvent, TBHN initiator (0.20equiv) in benzene added by syringe pump during 100min; C=acetal 4 dissolved in CH donor, bath temp 90°C, separate solutions of TBHN (0.20equiv) and of co-reactant in benzene added by syringe pump during 1h; D=acetal 4 and CH donor dissolved in benzene, otherwise as C.
^b Quin=Quinuclidine.
^c The initially-formed silyl ester was converted to the alkyl ester shown.^13
d Estimated by ¹H NMR spectroscopy.
^e Combined yield.
^f The low yield may reflect the relatively low boiling point (69°C) of diisopropyl ether.