Synthesis of sulfonimide-based dendrimers and dendrons possessing mixed 1 ? 2 and 1 ? 4 branching motifs Mykola Kolotylo a , Volodymyr Holovatiuk b , Julia Bondareva c , Oleg Lukin c,⇑ , Vladimir Rozhkov a,⇑ a Institute of Organic Chemistry, National Academy of Science, 5 Murmanskaya St., Kiev 02660, Ukraine b Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences, 50 Kharkovskoye Shosse, Kiev 02660, Ukraine c Skolkovo Institute of Science and Technology, 3 Nobel St., 143026 Moscow, Russia article info Article history: Received 24 October 2018 Revised 18 December 2018 Accepted 21 December 2018 Available online xxxx Keywords: Dendrimers Nitro compounds 1,3,5-Trinitrobenzene Sulfonyl chlorides Sulfonimides abstract The synthesis of dendrimers and a chlorosulfo-dendron possessing a unique combination of 1 ? 2 and 1 ? 4 branching types is described. The procedure consists of a two-step preparation of 3,5-dinitroben- zene-1-sulfonyl chloride, which was used for the persulfonylation of p-toluidine and 4-(benzylthio)ani- line. The obtained tetranitro compounds were reduced to the corresponding tetraamines. The latter were decorated with eight 4-toluene sulfonyl groups each to furnish the corresponding dendrimers. Oxidation of the dendrimer possessing a 4-(benzylthio)phenylene core with N-chlorosuccinimide resulted in the formation of a dendron with a sulfonyl chloride functionality at the focal point. Ó 2018 Elsevier Ltd. All rights reserved. Introduction The first series of ‘‘cascade molecules” was synthesized by Vögtle and co-workers in 1978 [1,2]. The term ‘‘cascade” was cho- sen because it evokes analogies to the repetitive branching of the arms and with some justification this type of molecule could have been called dendritic. These molecules were synthesized diver- gently utilizing two branching motifs. In 1985 Tomalia and co- workers developed branched poly(amidoamines) (PAMAM), coined, and propagated the name ‘‘dendrimer” [3,2]. PAMAM den- drimers were obtained by a divergent method involving the 1 ? 2 branching motif, which means every branching point is capable of attaching two branches or terminal groups. Fréchet and Hawker described the first convergent synthesis of dendrimers. They con- structed poly(arylether) architectures ‘‘from the outside inwards” applying again the 1 ? 2 branching type [4]. Newkome and co- workers, in turn, presented a divergent synthetic route to water- soluble, highly branched ‘‘arborol systems” with terminal hydroxyl groups. In this case, the 1 ? 3 branching motif was utilized [5]. Percec and co-workers described an original convergent synthesis of four generations of dendrons with the 1 ? 3 branching motif based on the AB 3 building block methyl 3,4,5-trishydroxybenzoate [6]. Müllen and co-workers reported the four-fold Diels–Alder reaction of functionalized tetraphenylcyclopentadienone (the so- called A 4 B building block) with tetraethynylbiphenyl leading to the first and thus far only type of dendrimer with a 1 ? 4 branch- ing motif [7]. Herein, we describe an alternative approach to the branched architectures involving combined 1 ? 2 and 1 ? 4 divergent growth type. Results and discussion The key compound for the preparation of the highly branched dendrons described in this work is 3,5-dinitrobenzene-1-sulfonyl chloride 2 (Scheme 1). Examination of the literature revealed that compound 2 could be obtained from 3,5-dinitroaniline via reaction with NaNO 2 with subsequent treatment of the diazonium salt with SO 2 [8]. However, this method has some drawbacks. Applying gas- eous SO 2 onto the diazonium salt solution complicates the synthe- sis. Additionally, 3,5-dinitroaniline is a rather expensive reagent. We developed a new two-step synthetic pathway to sulfonyl chloride 2 starting from 1,3,5-trinitrobenzene (TNB)(CAUTION: TNB is an explosive and should be handled with great care), the product of the primary processing of 2,4,6-trinitrotoluene. As shown in Scheme 1, in the first step the nucleophilic displacement of one nitro group in 1,3,5-trinitrobenzene with benzyl thiol in the presence of K 2 CO 3 takes place [9]. The process of the substitution https://doi.org/10.1016/j.tetlet.2018.12.052 0040-4039/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: o.lukin@skoltech.ru (O. Lukin), vladimir_rozhkov@mail.ru (V. Rozhkov). Tetrahedron Letters xxx (xxxx) xxx Contents lists available at ScienceDirect Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet Please cite this article as: M. Kolotylo, V. Holovatiuk, J. Bondareva et al., Synthesis of sulfonimide-based dendrimers and dendrons possessing mixed 1 ? 2 and 1 ? 4 branching motifs, Tetrahedron Letters, https://doi.org/10.1016/j.tetlet.2018.12.052