N-protected Indoles Research Articles

Asymmetric Binary Acid Catalysis: A Regioselectivity Switch between Enantioselective 1,2‐ and 1,4‐Addition through Different Counteranions of InIII

You can count on the anion: Simply swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2- and 1,4-addition reactions. N-protected indoles and β,γ-unsaturated α-keto esters gave adducts with excellent enantioselectivity (see scheme).

Iodine-Induced Regioselective C−C and C−N Bonds Formation of N-Protected Indoles

A mild, metal-free, and environmently benign iodine-promoted regioselective C-C and C-N bonds formation of N-protected indole derivatives giving 2,3'-biindoles 2 and 4-(1H-indol-2-yl)morpholines 4 is successfully demonstrated. Various bioactive 2,3'-biindoles and 4-(1H-indol-2-yl)morpholines, bearing electron-rich to moderately electron-poor substituents, can be prepared in moderate to good yields.

Asymmetric Hydrogenation of N-Protected Indoles Catalyzed by Iridium Complexes

In this work, several iridium complexes were developed to catalyze asymmetric hydrogenation of N-protected indoles which provided various indolines bearing C2 or C3 chirality in high yield and enantioselectivity. These catalysts were not only efficient but also practical in air and moisture stability.

Iridium‐Catalyzed Asymmetric Hydrogenation of N‐Protected Indoles

Chiral indolines substituted at C-2 or C-3 can be prepared in high yield and excellent enantioselectivity by asymmetric hydrogenation of N-protected indoles by using Ir catalysts with chiral N,P ligands. With less reactive substrates, the reaction had to be carried out at elevated temperature, but even at 60–110 °C very high enantiomeric excesses of up to 98–99 % could be obtained (see scheme).

Direct N- and C-alkenylation of nitrogen-containing heterocycles with magnesium alkylidene carbenoids

Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with N-lithio nitrogen-containing heterocycles gave N-alkenylated products in moderate to good yields. Also, the reaction of C-lithio indoles, which were generated from N-protected indoles, with magnesium alkylidene carbenoids gave C-2 or C-3 alkenylated products, corresponding to the protective group. The intermediate of these reactions were found to be the alkenyl anion, which could be trapped with electrophiles to give the heterocycles having fully substituted alkenes.

Palladium-Catalyzed Functionalization of Indoles with 2-Acetoxymethyl-Substituted Electron-Deficient Alkenes

New functionalizations of indoles via palladium-catalyzed reaction of indoles and 2-acetoxymethyl-substituted electron-deficient alkenes are reported. It was found that for N-protected indoles the reaction proceeded smoothly in the presence of 5 mol % of Pd(acac)2 and 10 mol % of PPh3 at 80 degrees C in HOAc, while for N-unprotected indoles, the reaction was carried out by using 5 mol % of Pd(dba)2 or 2.5 mol % of Pd2(dba)3.CHCl3 with 10 mol % of 2,2'-bipyridine as the catalyst in toluene. This strategy allows the selective installation of electron-deficient olefin functionality at the 3-position of indoles, which might be difficult to obtain by other methods and can be further elaborated.

Catalytic asymmetric hydrogenation of indoles using a rhodium complex with a chiral bisphosphine ligand PhTRAP

Highly enantioselective hydrogenation of N-protected indoles was successfully developed by use of the rhodium catalyst generated in situ from [Rh(nbd) 2]SbF 6 and the chiral bisphosphine PhTRAP, which can form a trans-chelate complex with a transition metal atom. The PhTRAP–rhodium catalyst required a base (e.g., Cs 2CO 3) for the achievement of high enantioselectivity. Various 2-substituted N-acetylindoles were converted into the corresponding chiral indolines with up to 95% ee. The hydrogenations of 3-substituted N-tosylindoles yielded indolines possessing a stereogenic center at the 3-position with high enantiomeric excesses (up to 98% ee).

Palladium‐Catalyzed Functionalization of Indoles with 2‐Acetoxymethyl‐Substituted Electron‐Deficient Alkenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

ChemInform Abstract: The First Synthesis of Mutagenic Trp-P-1 via the Electrocyclic Reaction of 1-Azahexa-1,3,5-triene System.

Reaction of the N-protected indole (I) with ethoxyethylidene Meldrum's acid (II) in the presence of a base followed by treatment with phenol (IV) yields the acrylic ester (V) which is converted into the ketoxime (XI).

Synthesis of alkyl-substituted N-protected indoles via acylation and reductive deoxygenation

La synthese d'alkyl-2-, -3- ou -5 benzenesulfonyl-1 indoles a ete effectuee par une reaction de Friedel-Graft suivie d'une desoxygenation

Vicinal Bromopropargoxylation of Cyclic Olefins and Cobaloxime-Mediated Heteroannulation to Functionalized 3-Methyleneoxacyclopentanes

The reaction of N-bromosuccinimide (NBS) and 2-propynol with cyclic olefins 1, including heteroaromatic benzofuran and N-protected indole, gave β-bromo-α-propargyl ethers 2. The adducts 2, some of which were quite sensitive, were cyclized with cobaloxime/sodium borohydride to give functionalized 3-methyleneoxacyclopentanes 3. The reaction sequence amounts to a simple two-step heteroannulation procedure

Synthesis and reactivity of 2-(1',3'dithian-2'-yl)indoles

The 2-(1',3'-dithian-2'-yl)indoles 1 a,b were prepared in a single operation involving reaction of the onions of the N-protected indoles 3 a,b with 2-chloro-1,3-dithiane. Subsequent reaction of 1 a with excess n-BuLi followed by an electrophile (1-methyl-4-piperidone) led to formation of the ring opened acetylene derivative 13 and not to the expected product 19 ( N -SO 2Ø). When t-BuLi was employed as the base the dithiane ring opened product 14 was obtained. Successful functionalization of the dithiane C-2' carbon was achieved giving compounds 16 – 20 on reaction of the dianion derived from 1 c and n-BuLi (2 equiv.) with an electrophile (Table 1 : yields : 70–90%).