The Spectrum of Indole

and N-H protons of indole (1) in carbon tetrachloride appear as triplets23 (Fig. 4A, p. 286), readily separable from each other and from the aromatic protons. The triplet structure shows that, like pyrrole,24-26 

The signal due to the 1-proton is broad owing to its coupling with the 14N nucleus (spin= 1) which has a short relaxation time presumably by 

Chemical Shifts and Coupling Constants of the Heterocyclic Ring of Indole0 

Signals Positions of resonance signals in t (ppm) Overall At Coupling constants, J in Hz 

The fact that the 2- and 3-protons are coupled to the N-H proton is further proved by the appearance of a pair of doublets when the 1-proton is deuterated (Fig. 2B). 

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Thus far, we have discovered and demonstrated a new and effident method for the synthesis of indoles from various carbonyl compounds. This, in conjunction with the use of alkyries in the palladium-catalyzed indolization, widens the spectrum of indoles that can be prepared by these means. The simple procedure, mild reaction conditions, and ready availability of the starting materials render these methods valuable additions to indole chemistry. We next extended this method to the synthesis of the indole core of a PGD2 receptor antagonist, laropiprant 3. 

The 13C shifts of the octahydroindolo[2,3-a]quinolizine [363] provide an important basis for the analysis of the 13C NMR spectra of the yohimbine and related group of alkaloids. The shifts shown in [363] (208) represent a revision of those originally made for C(9) and C(10) (225) since these were based on misassigned signals in the spectrum of indole itself (see Section XII.A). In addition, Wenkert (226) has suggested the interchange of the shifts for C(4) and C(6) and the correction has been made in [363]. 

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