Trichloroethoxycarbonyl reaction conditions

The silyl protective groups on the baccatin core structure were removed under reaction conditions. Bac3 Pi = H, P2 = Bz, P4 = Ac, P7 = Pio = 2,2,2-trichloroethoxycarbonyl. 

It has been reported that the reaction of NN-dimethylfuntumine (la) with trichloroethoxycarbonyl chloride gave the elimination product (2), in high yield, rather than the expected urethane (lb).4 Under the same reaction conditions the epimeric dimethylamino-pregnane derivatives (3a) and (3b) both gave the olefin (4), accompanied by minor amounts of the expected urethanes (3c) and (3d) respectively. The reaction of conessine (5a) with Cl3CCH2OCOCl yielded only the urethane (5b).4... 

The reactions described so far all yield medium-ring tertiary amines. Reinecke s group have recently extended their methods to synthesize the more useful secondary amines.288 Three syntheses were developed. The first [Eq. (31)] involves reductive cleavage of the benzyl indolizidinium salt 229 with lithium aluminum hydride, followed by replacement of the benzyl group with the labile trichloroethoxycarbonyl group. The latter may be removed under mild conditions with zinc-methanol, which does not cause migration of the double bond. 

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