Catalytic one-pot synthesis of [5.5.5.6]fenestrane systems via a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes.
Catalytic one-pot synthesis of fenestrane derivatives from dienediynes was developed: fenestranes were synthesized in high yields by a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes.
Rh(I)-catalyzed chemo- and stereoselective domino cycloaddition of optically active propargyl 2,4-hexadienyl ethers.
1,1'-Bi-2-naphthol in combination with ZnEt2, Ti(O(i)Pr)4, and dicyclohexylamine have been employed to catalyze asymmetric alkyne addition to an ynal to synthesize optically active propargylic alcohols containing two alkyne functions with excellent yields and enantioselectivities. These chiral alcohols are readily converted to the corresponding optically active propargyl 2,4-hexadienyl ethers. These diene-diyne substrates are found to undergo a highly chemoselective and stereoselective domino Pauson-Khand and Diels-Alder cycloaddition catalyzed by [RhCl(CO)2]2 under CO to generate a class of tetracyclic compounds with high enantiomeric purity. This is a very efficient method for the asymmetric synthesis of polycyclic compounds.
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more