A Regio and Diastereoselective Bromolactamization of d,g-Unsaturaterd Thioimidates

Organic Synthesis with N‐Heterocyclic Carbenes of Indazole: Synthesis of Benzo(thio)imidates, Benzo[d][1,3]thiazines and Quinazoline‐4‐thiones

“…The N-H proton gave a resonance frequency at approximately δ = 9.00 ppm which can be attributed to the H-bonded proton of the Z isomer. The signals of the N-Me group were detected between 3.29 ppm (3f) and 3.60 ppm (3c, 3e) in the 1 H NMR spectra taken in CDCl 3 . For the case of sterically demanding substituents as is the case for 3a,b as well as in isopropyl derivative 3d, a second set of signals is visible which can be attributed to the corresponding E isomers.…”

“…Thermal rearrangements of C2-unsubstituted 1H-benzo[d] [1,3]thiazin-4(2H)-imines into 2,3-dihydroquinazoline-4(1H)-thiones at 200°C over a period of 1 h have been previously reported. [55] The outcome of the reaction with propionaldehyde described here is very clearly governed by the electronic properties of the aniline ring.…”

“…This method of preparing 6a,e,f gives considerably better yields than reported. As an example, 6a was formed earlier in 45 % yield using ethanol as solvent, or in 15 % yield by reaction of benzo[d] [1,3]thiazine-4(2H)-thione with methylamine in benzene/ethanol mixtures. In this case, thioamide 5a was formed in 70 % yield as the main product.…”

“…[16][17][18] Nitriles can be coupled with thiols under acidic [19][20][21][22] or basic conditions. [23,24] The former mentioned reaction can be regarded as a modified Pinner the ring-opened intermediates into functionalized 2-anilinobenzamides which can be thionated with Lawesson's reagent and subsequently cyclized with formaldehyde and propionaldehyde, respectively, to give benzo [d] [1,3]thiazines and quinazoline-4-thiones. The outcome of the cyclization depends upon the thiobenzamide substitution pattern.…”

“…Their syntheses have been reviewed in 2005 by summarizing only 34 references. [1] Nevertheless, the synthetic potential of this functional group has been demonstrated by the preparation of several heterocyclic ring systems from suitable substituted thioimidates; among these are triazoles, [2] chiral pyrrolidinones, [3] thiazoles, [4] pyrroles, [5] 3,4-dihydro-2H-pyrroles, [6] pyrimidines, [7] dihydropyridines, [8] and 2-azabicyclo[3.2.0]hept-2-enes. [9] Furthermore, N,NЈ-unsymmetrically substituted 1,3-diketimines were prepared from thioimidates.…”