petasis reagent cp2TiMe2

titanocene dichloride 1 eq.
meli 2 eq. (can use excess)
-5 C, meli in Et2O was added dropwise into titanocene dichloride in toluene (0.1-0.2 M) during 10 min.
upon addition, red insoluable TiCP2Cl2 disappeared slowly.
an intermediate TiCp2ClMe is soluable and red colored.
the product ticp2me2 is also soluable but orange colored.

although standard prodcedure require 2 eq. of meli. I found out excee meli won't affect anything.

quench the rxn by nh4Cl solution;, then extract with Et2O. dried over mgso4 and concentrated to 0.5M (toluene). stored in freezer.

Tandem Semipinacol/Schmidt Reaction

Org. Lett., 8 (23), 5271 -5273, 2006.





A TiCl₄-promoted tandem semipinacol/Aube's type intramolecular Schmidt reaction of -siloxy-epoxy-azide has been designed and developed to be a general method for efficient construction of azaquaternary carbon units. As applicable examples, some key tricyclic azaquaternary skeletons incorporated in many important alkaloids, such as cephalotaxine, stemonamine, erythrinan, and homoerythrinan alkaloids, have been constructed.

petasis reagent: (cp)2Ti(cyclopropane)2

Cp2Ti(cyclopropane)2 is used to convert a ketone into cyclopropane-alkene.

1. making of this reagent.
Li,Et2O, 0 C, add cyclopropanebromide dropwise into the solution.( very exothermic).
low sodium Li can be used. 1hr at rt, then the solution was transfered into a Et2O solution of Cp2TiCl2 at 0 C. stirred for 90 min, quenched by ice water. washed, dried over MgSO4, concentrated. red solid. dissolved in toluene (0.5-0.8 mol/l). The solubility is poor in toluene, so can't make more concentrated). stored in freezer. Solid will be precipitated from the solution in the freezer, so warm it up before use.

2. reaction.
usually, 3-5 eq. of the reagent, toluene as solvent, 50-55C. overnight.
the product is very easy to isomerize to other alkene-isomers. So during the reaction, some NaHCO3 solid can bee added to prevent isomerization.