Umlagerung und Abbau bicyclischer Amin—Tetraorganodiboroxane [1]

Rearrangement and Degradation of Bicyclic Amine‐Tetraalkyldiboroxanes [1] The amine‐tetraalkyldiboroxanes [ 1a : R 1,4,7,7′ = Et; 1b : R 1,4,7 = Et, R 7′ = Ph; 1b′ : R 4,7,7′ = Et,R 1 = Ph; 1c : R 1,7,7′ = Et, R 4 = Ph] react on heating by EtBO elimination and allylborane rearrangement to yield the allyl‐aminoboranes Me 2 NB(Et)CH 2 C(R 4 )=C(R 7,7′ ) [ 2a: R 4,7,7′ = Et; 2b/2b ′: R 4 = Et, R 7,7′ = Et, Ph; 2c : R 4 = Ph, R 7,7′ = Et]: On heating above 60°C the diastereomeric syn/anti‐ Id/1d′ (Id : R 1,7 = C 8 H 14 , R 4,7′ = Et; 1d′ : R 1,7′ = C 8 H 14 , R 4,7 = Et) give the unsaturated rac ‐amino‐trialkyldiboroxane ( rac ‐ 3 ) (X‐ray structure analysis) by intramolecular 1,2‐deaminoboration. rac‐ 3 is characterized by reaction with (Et 2 BH) 2 and (Et 2 BD) 2 with formation of the 1,2,6‐oxadiborinane 5 by evolution of H 2 or HD respectively. The intramolecular CH‐borylation of rac ‐ 3 is compared with those of the thujopsen hydrocarbons I–III.