Substituted 1,3,2,4‐benzodithiadiazines: Novel derivatives, by‐products, and intermediates*

Abstract

Abstract The synthesis of the title compounds 1 by 1 : 1 condensation of ArNSNSiMe 3 2 with SCl 2 followed by intramolecular ortho‐cyclization of each [ArNSNSCl] intermediate is complicated by further reaction of 1 with SCl 2 to give Herz salts 3 . With the 2 :SCl 2 ratio of 2:1, the formation of by‐products 3 is reduced and novel compounds 1 are accessible. With ortho‐I containing starting material 2j , the parent compound 1s is obtained as the result of an unexpected I, not H, substitution. The rate of the 1 + SCl 2 reaction depends upon a substituent's position, and the minor 8‐R isomers 1l,p (R = Br, I) are isolated for the first time from mixtures with the major 6‐R isomers due to reduced reactivity toward SCl 2 . The synthesized compounds 1–3 are characterized by multinuclear (including nitrogen) NMR and X‐ray crystallography. According to the X‐ray diffraction data, 1j (6‐Br) and 1k (7‐Br) derivatives are planar, whereas 1i (5‐Br) and 1l (8‐Br) are bent along the S1···N4 line by ∼5° and ∼4°, respectively, and the 1r (7‐OCH 3 ) derivative is planar in contrast to the known 5‐OCH 3 isomer, which possesses a significantly folded heterocycle. The distortion of the planar geometry of some compounds 1 is interpreted in terms of a pseudo‐Jahn‐Teller effect as the result of π‐highest occupied molecular orbital (HOMO)  σ*‐(LUMO) lowest unoccupied molecular orbital + 1 mixing in a planar conformation. The 2p compound is the first structurally defined Ar–N = S = N–SiMe 3 azathiene. The compound Ar–N = S = N–S–NH‐Ar 6 modeling the aforementioned intermediate has been isolated and structurally characterized. We describe the attempts to synthesize compounds 1 from 2‐aminobenzenethiols and (SN) 4 and from salts 3 and Me 3 SiN 3 , and we discuss the reaction pathways. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:563–576, 2001