ABSTRACT
A number of new nido-carboranyl amidines 10-R(CH2)nNHC(Et)[double bond, length as m-dash]HN-7,8-C2B9H11 (n = 2, R = OH, OMe, and NMe2; n = 3, R = OH) were synthesized by the nucleophilic addition of amino alcohols and N,N-dimethylethylenediamine to the highly activated -C[triple bond, length as m-dash]N+- triple bond of the 10-propionitrilium derivative of nido-carborane. A similar reaction of 10-EtC[triple bond, length as m-dash]N-7,8-C2B9H11 with ethylenediamine unexpectedly resulted in the cleavage of the C[triple bond, length as m-dash]N bond to form the ammonium derivative 10-H3N-7,8-C2B9H11. The complexation of the synthesized carboranyl amidines 10-MeO(CH2)2NHC(Et)[double bond, length as m-dash]HN-7,8-C2B9H11 and 10-Me2N(CH2)2NHC(Et)[double bond, length as m-dash]HN-7,8-C2B9H11 with nickel and palladium phosphine complexes [(Ph3P)2MCl2] (M = Ni, Pd) was studied. The reactions with 10-MeO(CH2)2NHC(Et)[double bond, length as m-dash]HN-7,8-C2B9H11 result in half-sandwiched metallacarborane complexes with the retention of one triphenylphosphine ligand [3-Ph3P-3-(8-MeOCH2CH2N[double bond, length as m-dash]C(Et)NH)-3,1,2-MC2B9H10], while the reactions with 10-Me2N(CH2)2NHC(Et)[double bond, length as m-dash]HN-7,8-C2B9H11 proceed with the complete loss of the phosphine ligands and lead to the formation of complexes with the η5:κ2(N,N')-coordinated carboranyl amidine ligand [3,3-(8-Me2NCH2CH2N[double bond, length as m-dash]C(Et)NH)-3,1,2-MC2B9H10]. The crystal molecular structures of the synthesized complexes were determined by single crystal X-ray diffraction.
ABSTRACT
Stereospecific oxidation of diacetoxyheterobetulin with ozone and dimethyldioxirane led to 3ß,28-diacetoxy-18α,19ßH-urs-20α,21α-epoxide with yields of 79% and 87%, respectively. Oxidation with ozone was not selective and gave two minor products containing 2lα-hydroxy-20(30)-ene and 21a-hydroxy-20ß,28-epoxy-fragments in ring E. The structures of 3ß,28-diacetoxy-18α,19ßH-urs-20α,21α-epoxide and 3ß-diacetoxy-21α-hydroxy-20ß,28-epoxy-18α,19ßH-ursane were confirmed by X-ray analysis for the first time.
