Synthesis of germatranyl derivatives of esters of carboxylic acids via organometallic (Si, Ge, Sn) reagents

Article abstract of DOI:10.1002/cber.19971300611

Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH₂CHROSnAlk₃)₃ (9-11) (R = H, Me; Alk = Et, Bu), react with X₃GeC(R¹)H(R²)COOR³ (12-17) (X = Cl or Br; R¹, R² = H, Me, Ph, SiMe₃, COOEt; R³ = Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH₂CHRO)₃GeQ(R¹)MR²)-COOR ³ (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et₃SnOMe to give in situ Et₃SnC(Ph₂)COOMe (23), followed by reaction with GeCL, to give in situ Cl₃GeC(Ph₂)COOMe (22) and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH₄ in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6, and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively. VCH Verlagsgesellschaft mbH,.