Geranylamine diethyl

Like the synthesis of L-DOPA by asymmetric hydrogenation, the manufacture of L-menthol hy Takasago Company is also one of the early examples of an industrial process where asymmetric isomerization is a key step. The desired isomerization reaction is one of the steps of the overall synthetic scheme. The synthesis of L-menthol from diethyl geranylamine is shown by 9.2. The formal electron pair pushing mechanism for the isomerization of the allylic amine to the enamine proceeds according to reaction 9.3. 

The key step of this process is the asymmetric isomerization of (A,A)-diethyl-geranylamine or diethylnerylamine to give (7 )-citronellal ( )-diethylenamine. 

Recently it has become known from work at Firmenich, that BINAP can be effectively replaced by the Josiphos and Daniphos ligands. [129] From diethyl-geranylamine one obtains after hydrolysis (S>citronellal, and from diethyl-nerylamine (R)-citronellal (analogous to (R)-BINAP). By attaching a linker to the unsubstituted cyclopentadiene ring, the catalyst can be immobilised on various carriers. In some cases this reduces the activity, but the stereoselectivity remains comparable. 

An extensive two-part review of enamine chemistry has appeared, covering synthetic methods as well as reactivity and physical organic aspects. A survey of the chemistry of amino-arsanes includes a review of their use in the preparation of enamines. A highly enantioselective hydrogen migration has been observed in the isomerization of A A -diethyl-nerylamine and -geranylamine in the presence of a chiral rhodium(i) catalyst, giving the optically active ( )-enamine [equation (11)]. ... 

---