## 2 Results and Discussion
Under the same conditions, the reactions of sulfenyl chloride **3** with \(1H\)-indene afforded the condensed five-membered product in only a 43% yield. Refluxing the reaction mixture resulted in the formation of a small amount of by-product along with the target compound. However, when the reaction time was increased to 65 h at room temperature, pure annulation product **12** was obtained in an 80% yield (Scheme 6). The reaction of sulfenyl chloride **3** with 4-methylstyrene was carried out at room temperature for 24 h in methylene chloride affording compound **13** in quantitative yield (Scheme 7). Under the same conditions as the synthesis of product **13**, the reaction of sulfenyl chloride **3** with \(\alpha\)-methylstyrene gave annulation product **14** in an 87% yield (Scheme 7). The reaction of sulfenyl chloride **3** with \(\alpha\)-methylstyrene seems to proceed more slowly than with 4-methylstyrene and styrene. The methyl substituent at position 4 of the benzene ring has little influence on the yield of the product, and compounds **11** and **13** (derived from both styrene and 4-methylstyrene) were obtained in 97% and quantitative yields, while the introduction of the methyl substituent to the \(\alpha\)-position of the double bond affects on the annulation reaction and slightly decreases the the annulation product yield to 87% under the same conditions. All the studied substrates can be schematically divided into two groups: terminal alkenes including allyl arenes and styrene derivatives, which contain the double bond in conjugation with the benzene ring. In general, the latter group of compounds demonstrates the higher activity in the annulation reactions compared to the terminal alkenes (Scheme 8). The annulation reactions with the terminal alkenes, whose double bond is not in conjugation with the benzene ring, proceed with the attachment of the sulfur atom of sulfenyl halides 3, 4 at the \(\alpha\)-position of the double bond (the anti-Markovnikov direction). In the case of styrene derivatives, the addition of the sulfur atom occurs at the terminal carbon atom of the double bond (the Markovnikov direction). Possible intermediates **A** and **B**, which correspond to two directions of these reactions, can be considered for the explanation of these trends (Scheme 8). We assume that the reactions with terminal alkenes proceed via three-membered thirianium intermediates **A**. It is known that the electrophilic addition reactions of sulfenyl chlorides [41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54] with linear 1-alkene mainly give anti-Markovnikov products [41; 42; 43], and thirianium cations are regarded as intermediates of these reactions [42; 43; 44; 45]). Nucleophilic attack of the nitrogen atom of the quinoline ring occurs at the unsubstituted carbon atom of thirianium intermediates **A** due to the steric factor, which determines the anti-Markovnikov direction of the reactions (Scheme 8). It is assumed that linear carbocations **B** are involved as intermediates in the reactions with styrene derivatives. In this case, linear carbocations **B** are energetically favorable due to their stabilization by the benzene ring that provides the Markovnikov direction of the reactions (Scheme 8). It is known that electrophilic addition of sulfenyl chlorides to styrene leads to Markovnikov products [52; 53]. The antibacterial activity of the synthesized compounds was evaluated. The minimal inhibitory concentration (MIC) was determined using the broth standard microdilution method [55]. The obtained results are presented in Table 1. Compounds **1**, **5**-**14** were tested in vitro for antimicrobial activity against strains of the Gram-positive bacteria _Bacillus subtilis_ B-406 and _Enterococcus durans_ B-603 (which are similar in properties and taxonomic affiliation to bacteria _Staphylococcus aureus_) and the Gram-negative bacteria _Escherichia coli_ B-1238 (the bacterial strains were taken from the All-Russian Collection of Microorganisms).