Piperidines, hydroamination produces

Hydroamination of olefins under most catalytic conditions proceed with Markovnikov addition of the N-H bond across the olefin. Shown below is a rhodium-catalyzed intramolecular, anti-Markovnikov, hydroamination developed for the synthesis of 3-arylpiperidines 167 <06JA6042>. Further evaluation of this reaction as a synthesis of multisubstituted piperidines revealed that substrates with substituents a or y to the amino group did not produce the expected piperidine, however, substrates with a substituent (1 to the amino group produce piperidines in high yield. 

An interesting example of a gold-catalyzed cycloisomerization of P-aminoallene 168 to tetrahydropyridine 169 is depicted below <06OL4485>. Patil et al. report a similar gold-catalized hydroamination of allenes to produce 2-vinyl piperidine 170 in good yield <06TL4749>. 

Intramolecular hydroamination of aminoalkenes CH2=CH(CH2) CH2NH2 and the corresponding alkynes can be catalysed by the calcium /9-diketiminato complex [ HC (C(Me)2N-2,6-Pr2C6H3)2 Ca N(SiMe3)2 (THF)] to produce the corresponding pyrrolidines and piperidines.71... 

Complexes 213 and 203 bearing the same enantiopure binaphthyldiamide ligand were compared for the catalysis of several hydroamination reactions with various substrates. The comparison showed differences in activity and/or selectivity in two catalytic systems. The results indicate that different active species are involved. Both complexes produce pyrrolidines and piperidines with moderate to high enantioselectivity and their catalytic activity are comparable [162]. 

Chiral epoxide 56 was opened with suitable alkyne 57 (bearing alkyl chain present in the tail of the alkaloid) followed by TBS protection of alcohol that provides diamine 59. Diamine 59 undergoes Ag-catalyzed reductive hydroamination to produce piperidine ring 60 with correct stereochemistry as present in the alkaloid. Finally, the TBS group is deprotected to produce (-p)-pseudodistomine D 61 in quantitative yield (Scheme 39.15). 

The iron hydride complex FeH(CO)(NO)(Ph3P)2 has been reported to catalyse selective hydrosilylation of internal alkynes Ar C=CAr with PhSiHj. The corresponding intermediate (Z)-vinylsilanes Ar CH=C(SiH2Ph)Ar thus generated then produce trans-Ar CH=CHAr. With PhMeSi(H)CH=CH2 as the reagent, di-Ar CH=CHAr were obtained. Mechanistic details of this stereodivergent method have been diseussed. Tetrahydropyrans and piperidines (218) were obtained by the Fe -catalysed intramolecular hydroalkoxylation and hydroamination of allenes (217). ... 

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