124292-15-5Relevant academic research and scientific papers
Atomic motions and protonation stereochemistry in nucleophilic additions to bicyclobutanes
Hoz, Shmaryahu,Azran, Carmela,Sella, Ariel
, p. 5456 - 5461 (2007/10/03)
Several nucleophilic reactions on bicyclobutanes activated at the gehead carbon by electron withdrawing groups (SO2Ph, CO2Me, COPh, and CN) were performed in MeOH. In all cases, the less stable 1,3-disubstituted cyclobutanes isomer was preferentially obtained (compared to the equilibrium ratio). The results for the two charge localizing groups CN and SO2Ph oppose the existing knowledge regarding the protonation stereochemistry of such carbanions. Ab initio calculations (6-31G*) have shown that as the nucleophile approaches the bicyclobutane, the bridgehead activating group moves inward toward an axial position. With a charge localizing group (CN and S(H)SO2) the carbanion remains pyramidal, whereas with C(H)=O as an activating group, the carbanion is nearly planar. It is suggested therefore that under conditions where the carbanion undergoes rapid protonation, it is trapped in its initial pyramidal geometry. Whereas, in cases where the lifetime of the carbamon is long enough to allow appreciable equilibration, protonation may result in a different product distribution. This hypothesis was tested by slowing down the protonation rates. As a result, the more stable isomer was indeed preferentially obtained.
NEW BRIDGEHEAD-SUBSTITUTED 1-(ARYLSULFONYL)BICYCLOBUTANES AND SOME NOVEL ADDITION REACTIONS OF THE BICYCLIC SYSTEM
Gaoni, Yehiel
, p. 2819 - 2840 (2007/10/02)
In view of planned syntheses of target cyclobutane derivatives, a series of new 3-substituted bicyclobutanes was prepared from sulfones 1-7.Some novel addition reactions involving the central bond were then applied to several of the new compounds as well
