Unique Stereocontrol in Carborane Chemistry: Skeletal Alkylcarbonation (SAC) versus Exoskeletal Alkylmethylation (EAM) Reactions |
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| Authors: | Dr Mario Bakardjiev Dr Josef Holub Dr Jan Macháček Dr Drahomír Hnyk Prof Dr Bohumil Štíbr Dr Zdeňka Růžičková Prof Dr Aleš Růžička |
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| Institution: | 1. Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, Husinec‐?e? 1001 (Czech Republic);2. Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice (Czech Republic) |
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| Abstract: | Reactions between the arachno‐6,9‐C2B8H14 ( 1 ) dicarbaborane and acyl chlorides, RCOCl ( 2 ), are subject to stereocontrol that completely changes the nature of the reaction products. While most chlorides produce the 8‐R‐nido‐7,8,9‐C3B8H11 ( 3 ) tricarbollides (by skeletal alkylcarbonation=SAC), bulky RCOCls ( 2 ; where R=1‐adamantyl, 2 a ; 1‐mesityl, 2 b ; 9‐anthranyl, 2 c ; 1‐naphthyl, 2 d ) in 1,2‐dichloroethane (DCE) in the presence of triethylamine at 40–60 °C gave a series of entirely different 1‐R‐2‐CH3‐closo‐1,6‐C2B8H8 ( 4 ) dicarbaboranes upon acidification with conc. H2SO4 (by exosleletal alkylmehylation=EAM). Both types of reactions seem to proceed via a common 8‐R‐nido‐7,8,9‐C3B8H10]? ( 3? ) anion which in the EAM case is unstable because of steric crowd and undergoes rearrangement via the isomeric R‐nido‐7,8,10‐C3B8H10]? tricarbollide structures which, on protonation, undergo reductive extraction of one CH vertex to generate the 2‐CH3 substituent in structure 4 . |
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| Keywords: | carboranes dicarbaboranes NMR spectroscopy stereocontrol tricarbaboranes |
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