Highly Regioselective Bromination of [3aR-(3aα,4β,7β,7aα)]-Hexahydro-7,8,8- trimethyl-4,7-methanobenzofuran-2(3H)-one via Nonclassical Bornyl Cations

Formaldehyde—A Key Monad of the Biomolecular System

“…The effect of enantiomer selectivity was also observed in ether formation [ 45 , 46 ], thioacetal and thioether formation [ 47 ] and in 1,4-addition of amines [ 48 , 49 ]. Added steric hindrance led to increased enantiomer selectivities of up to 14:1 [ 50 , 51 , 52 ]. We stated that as a rule in reactions involving connecting two chiral centers by an electron donating atom (like oxygen or sulphur) of two reaction partners each featuring a bulky substituent (e.g., alkyl), a σ * - or π * -receptor substituent (e.g., aryl or oxygen) and hydrogen at the chiral center, the diastereomer with like relative configuration of the three substituents will be preferentially formed once equilibrium is reached under reversible reaction conditions.…”