Organolanthanide complexes of the general type Cp'(2)LnCH(TMS)(2) (Cp' = eta(5)-Me(5)C(5); Ln = La, Sm, Y; TMS = SiMe(3)) and CGCSmN(TMS)(2) (CGC = Me(2)Si(eta(5)-Me(4)C(5))((t)()BuN)) serve as effective precatalysts for the rapid, regioselective, and highly diastereoselective intramolecular hydroamination/cyclization of primary and secondary amines tethered to conjugated dienes. The rates of aminodiene cyclizations are significantly more rapid than those of the corresponding aminoalkenes. This dienyl group rate enhancement as well as substituent group (R) effects on turnover frequencies is consistent with proposed transition state electronic demands. Kinetic and mechanistic data parallel monosubstituted aminoalkene hydroamination/cyclization, with turnover-limiting C=C insertion into the Ln-N bond to presumably form an Ln-eta(3) allyl intermediate, followed by rapid protonolysis of the resulting Ln-C linkage. The rate law is first-order in [catalyst] and zero-order in [aminodiene]. However, depending on the particular substrate and catalyst combination, deviations from zero-order kinetic behavior reflect competitive product inhibition or self-inhibition by substrate. Lanthanide ionic radius effects and ancillary ligation effects on turnover frequencies suggest a sterically more demanding Ln-N insertion step than in aminoalkene cyclohydroamination, while a substantially more negative DeltaS( double dagger ) implies a more highly organized transition state. Good to excellent diastereoselectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de). Formation of 2-(prop-1-enyl)piperidine using the chiral C(1)-symmetric precatalyst (S)-Me(2)Si(OHF)(CpR)SmN(TMS)(2) (OHF = eta(5)-octahydrofluorenyl; Cp = eta(5)-C(5)H(3); R = (-)-menthyl) proceeds with up to 71% ee. The highly stereoselective feature of aminodiene cyclization is demonstrated by concise syntheses of naturally occurring alkaloids, (+/-)-pinidine and (+)-coniine from simple diene precursors.

Intramolecular Hydroamination/Cyclization of Conjugated Aminodienes Catalyzed by Organolanthanide Complexes. Scope, Diastereo- and Enantioselectivity, and Reaction Mechanism

Syntheses of the sedum and related alkaloids

History, chemistry and biology of alkaloids from Lobelia inflata

An improved protocol for the construction of enantioenriched pyrrolidine, indoline, and piperidine rings using an organocatalyzed, intramolecular heteroatom Michael addition is described. Application to the enantioselective synthesis of homoproline, homopipecolic acid, and pelletierine has been accomplished.

Improved Protocol for Asymmetric, Intramolecular Heteroatom Michael Addition Using Organocatalysis: Enantioselective Syntheses of Homoproline, Pelletierine, and Homopipecolic Acid

Multiple stereoselectivity and its application in organic synthesis

A new asymmetric route to 2-substituted piperidines involving the Sharpless asymmetric dihydroxylation (AD) of 5-hexenylazide 1 and an intramolecular aminocyclization as crucial steps and its application to the asymmetric synthesis of four piperidine alkaloids, (+)-coniine 2, (−)-pelletierine 3, (+)-δ-coniceine 4, and (+)-epidihydropinidine 5 is presented.

A new asymmetric entry to 2-substituted piperidines. A concise synthesis of (+)-coniine, (−)-pelletierine, (+)-δ-coniceine, and (+)-epidihydropinidine

A new strategy has been developed for the synthesis of C2-symmetric trans-α,α‘-bis(hydroxymethyl)pyrrolidine and piperidine derivatives 1−3 starting from symmetric α,ω-terminal dienes 4−6. The doub...

Symmetry-Assisted Synthesis of C2-Symmetric trans-α,α‘-Bis(hydroxymethyl)pyrrolidine and -piperidine Derivatives via Double Sharpless Asymmetric Dihydroxylation of α,ω-Terminal Dienes†

Total synthesis of pyrrolizidines 223H', 239K', 265H', and 267H' found in Madagascan frogs (Mantella) and their affinities for nicotinic acetylcholine receptor.

Symmetry-Assisted Synthesis of C2-Symmetric trans-α,α′-Bis(hydroxymethyl)pyrrolidine and -piperidine Derivatives via Double Sharpless Asymmetric Dihydroxylation of α,ω-Terminal Dienes.

The asymmetric synthesis of pyrrolizidines 223H', 239K', 265H', and 267H' has been achieved starting from 1,5-hexadiene via a common synthetic intermediate 5. The affinity of both enanthiomers of 1-4 for nicotinic acetylcholine receptor was evaluated.

Catalytic asymmetric synthesis of both enantiomers of pyrrolizidines 223H', 239K', 265H', and 267H' found in Madagascan frogs (Mantella) and their affinities for nicotinic acetylcholine receptor

Seiki Takahashi

Papers

A new asymmetric entry to 2-substituted piperidines. A concise synthesis of (+)-coniine, (−)-pelletierine, (+)-δ-coniceine, and (+)-epidihydropinidine

Symmetry-Assisted Synthesis of C2-Symmetric trans-α,α‘-Bis(hydroxymethyl)pyrrolidine and -piperidine Derivatives via Double Sharpless Asymmetric Dihydroxylation of α,ω-Terminal Dienes†

Total synthesis of pyrrolizidines 223H', 239K', 265H', and 267H' found in Madagascan frogs (Mantella) and their affinities for nicotinic acetylcholine receptor.

Symmetry-Assisted Synthesis of C2-Symmetric trans-α,α′-Bis(hydroxymethyl)pyrrolidine and -piperidine Derivatives via Double Sharpless Asymmetric Dihydroxylation of α,ω-Terminal Dienes.

Catalytic asymmetric synthesis of both enantiomers of pyrrolizidines 223H', 239K', 265H', and 267H' found in Madagascan frogs (Mantella) and their affinities for nicotinic acetylcholine receptor