(S)-2-Benzyl-N-(2,6-diisopropylphenyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxamide

The asymmetric unit of the title compound, C29H34N2O, contains two molecules in which the N-containing six-membered rings assume different conformations viz. half-chair and envelope. Intermolecular N—H⋯O hydrogen bonding via the amide groups cross-link the molecules in the crystal structure.


Comment
The title compound is a precursor in the synthesis of novel chiral catalysts containing a tetrahydroisoquinoline framework (TIQ). Upon oxidation of the secondary amine, the N-oxide form of this compound and its derivatives are currently being tested as novel organocatalysts for asymmetric allylation reactions (Naicker et al. 2010).
The structure has two molecules in the asymmetric unit (Fig. 1). These molecules are linked via various intermolecular short contact interactions (2.01-2.83 Å). The crystal packing reveals that a hydrogen bond via the amide groups N2A-H2A···O1B link the molecules together resulting in a one-dimensional sheet along the c axis ( Fig. 2), also see (Naicker et al. 2011) From the crystal structure it is evident that the N-containing six membered rings assume different conformations for the two molecules in the asymmetric unit (Fig. 1). The ring containing N1A adopts a half chair conformation while N1B exists as a half boat conformation.

Experimental
(S)-2-Benzyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (1.5 g, 3.4 mmol) was dissolved in dry dichloromethane (15 ml) followed by the addition of triethylamine (2.0 eq.) and ethylchloroformate (1.2 eq.) which was stirred for 1 h at 0 degrees followed by the addition of 2,6-diisopropylaniline (1.1 eq.). The reaction mixture was then stirred at room temperature until no more starting material could be detected by TLC analysis (approximately 3 h). The reaction mixture was poured into water (30 equivalent volumes); the mixture was then extracted twice with dichloromethane (20 ml). The extracts were combined, dried over anhydrous magnesium sulfate and then concentrated to dryness affording the crude product which was purified by silica column chromatography (hexane:ethylacetate 80:20 R f =0.6).
supplementary materials sup-2 The absolute configuration was confirmed by NMR studies.

Figures
where P = ( Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.