Transition Metal-Diene Complexes in Organic Synthesis; Part 6.¹Stereoselective Synthesis of Iron-Complexed 4b,8a-Dihydrocarbazol-3-ones: A Novel Route to 4a,9a-Dihydro-9H-carbazoles and Highly Chemo-, Regio-, and Stereoselective Sakurai Reactions

Aluminum Chloride Catalyzed Stereoselective [3 + 2] Cycloaddition of Allylsilanes with Simple Conjugated Dienes

“…Lewis acids, such as boron trifluoride etherate, titanium tetrachloride, − etc., have been known to be effective catalysts for the [3 + 2] cycloaddition of activated α,β-unsaturated ketones with allylsilanes. However, the [3 + 2] cycloaddition of dienes with allylsilanes did not occur with Lewis acid catalysts other than aluminum chloride, indicating the requirement of a strong Lewis acid for the allylsilylations. − When chlorotrimethylsilane was used as an acivator to the aluminum chloride catalyst, a higher yield and faster reaction rate were observed, consistent with the previous results obtained from the allylsilylation of diallylsilanes .…”

“…A Lewis-acid-promoted [3 + 2] cycloaddition reaction in which an allylsilane serves as the three-carbon unit is an attractive approach to five-membered ring systems, which are found in a variety of important natural products . Since the [3 + 2] cycloaddition of an allylsilane with an α,β-enone catalyzed by titanium chloride was first reported by Knölker and co-workers in 1990, several examples of this [3 + 2] annulation of allylsilanes with other conjugated carbonyl compounds have been reported. − …”

Isolation and Synthesis of Biologically Active Carbazole Alkaloids

“…Oxidative cyclization of the quinone imines 23 using very active manganese dioxide affords stereoselectively the cyclized quinone imines 24, which are tricarbonyliron-complexed 4b,8a-dihydrocarbazol-3-ones. 36 Demetalation of the tricarbonyliron-complexed 4b,8a-dihydrocarbazol-3ones 24 using trimethylamine N-oxide 37 provides directly the 3-hydroxycarbazoles 25a. Finally, the 3-hydroxycarbazoles 25a can be transformed to the 3-methoxycarbazoles 25b by selective O-methylation (Scheme 5).…”

Transition Metal‐Diene Complexes in Organic Synthesis. Part 15. Iron‐mediated total synthesis of carbazomycin A and B

“…[12e] [30]) demonstrates once again the efficiency of this method for the synthesis of highly donor-substituted carbazole alkaloids.…”

“…-The formation of the cyclized Fe-complexed quinone imine 26 as by-product of the Fe-mediated arylamine cyclization suggested that this final step could be improved by taking advantage of the Fe-mediated quinone-imine cyclization. This latter process has already proven its enormous potential in the syntheses of various 4-unsubstituted carbazole derivatives [30],…”