ABSTRACT
[Structure: see text] The development of a concise enantioselective synthesis of nicotinic alkaloid 1 is presented. The route features the synthesis and use of a "stable" aliphatic triflate 21 in an alkylation step to generate Heck precursor 24 and an enantioselective cyclization to establish a compound with the key [3.2.1]-bicyclic core, 29.
Subject(s)
Molecular Probes , Nicotine/analogs & derivatives , Receptors, Nicotinic/chemistry , Crystallography, X-Ray , Models, Molecular , Nicotine/chemical synthesis , StereoisomerismABSTRACT
A novel palladium-catalyzed arylation of ketone enolates with o-nitrohaloarenes was achieved through the addition of phenol additives. The mild reaction conditions employed allowed for the inclusion of a wide variety of functional groups in both substrates to be tolerated. The products of this reaction were then readily reductively cyclized to give highly substituted indoles in moderate to excellent overall yields.
Subject(s)
Indoles/chemical synthesis , Ketones/chemistry , Phenols/chemistry , Benzene Derivatives/chemistry , Bromobenzenes/chemistry , Catalysis , Hydrocarbons, Halogenated/chemistry , Organometallic Compounds/chemistry , Palladium/chemistryABSTRACT
6Li and (13)C NMR spectroscopic studies were carried out on [(6)Li]n-BuLi and [(6)Li]PhLi (RLi) in toluene-d(8) containing the following diamines: N,N,N',N'-tetramethylethylenediamine (TMEDA), N,N,N',N'-tetraethylethylenediamine, 1,2-dipyrrolidinoethane, 1,2-dipiperidinoethane, N,N,N',N'-tetramethylpropanediamine, trans-(R,R)-N,N,N',N'-tetramethylcyclohexanediamine, and (-)-sparteine. Dimers of general structure (RLi)(2)S(2) (S = chelating diamine) are formed in each case. Treatment of RLi with two different diamines (S and S') affords homosolvates (RLi)(2)S(2) and (RLi)(2)S'(2) along with a heterosolvate (RLi)(2)SS'. Relative binding constants and associated free energies for the sequential solvent substitutions are obtained by competing pairs of diamines. The high relative stabilities of certain heterosolvates indicate that solvent binding to the RLi dimer can be highly correlated. Rate studies of both the 1,2-addition of RLi/TMEDA to the N-isopropylimine of cyclohexane carboxaldehyde and the RLi/TMEDA-mediated alpha-lithiation of the N-isopropylimine of cyclohexanone reveal monomer-based transition structures, [(RLi)(TMEDA)(imine)], in all cases. The complex relationships of solvent binding constants and relative reactivities toward 1,2-additions and alpha-lithiations are discussed.
