Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• alkyl group, direct dehydration was not possible because of blocking. Later they reported a similar transformation of thiiranes to provide a wide variety of substituted thiophenes. They had synthesized substituted thiophenes 133b starting from thiiranes 131b via cyclization utilizing the catalytic

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• [19]. The ring-contractions of five and six-membered aliphatic thiaheterocycles have been seldom applied in the preparation of thiatetraoses [20][21]. In contrast, both nucleophilic and electrophilic ring expansions of thiiranes have been developed to synthesize thietanes [22][23]. Phosphorodithioate

• thietane-2-ylideneacetates 397 as byproducts [104] (Scheme 83). 4. Synthesis via the ring expansions and contractions 4.1 Synthesis via ring expansion The ring expansions of thiiranes are alternative ways to prepare thietane derivatives. The transformations included the nucleophilic ring expansion of (1

• -haloalkyl)thiiranes with various nucleophiles, nucleophilic ring expansion of thiiranes with sulfur ylides, and the electrophilic ring expansion of thiiranes with carbenes generated from sulfur ylides under the catalysis of transition-metal catalysts. 4.1.1 Synthesis via nucleophilic ring expansion of 2-(1

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

• Grzegorz Mlostoń,
• Mateusz Kowalczyk,
• André U. Augustin,
• Peter G. Jones and
• Daniel B. Werz

Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109

• used with no special precautions. In general, ferrocene has been considered as an ‘exceptional compound’ [16][17] and in our hands ferrocenyl-functionalized sulfur heterocycles, e.g., thiiranes and 1,3-dithiolanes, have found applications for the synthesis of compounds relevant for medicinal [18] and

Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonyl S-methanides as diradical processes: a computational study

• Michael L. McKee,
• Grzegorz Mlostoń,
• Katarzyna Urbaniak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 410–416, doi:10.3762/bjoc.13.44

• (tetrahydrothiophenes) [6]. In the absence of a suitable dipolarophile, thiocarbonyl S-methanides 1 undergo either 1,3-dipolar electrocyclizations to give the isomeric thiiranes 3 or dimerize leading to five- or six-membered S-heterocycles (Scheme 1) [1][2]. The type of the dimeric product depends on the substituents

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

• Grzegorz Mlostoń,
• Paulina Pipiak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 716–724, doi:10.3762/bjoc.12.71

• products of the [3 + 2]-cycloaddition of the diazo dipole onto the C=S bond. The latter decompose only at higher temperature (ca. −40 °C) to generate thiocarbonyl S-isopropanide. In the absence of the starting thioketone, the corresponding thiiranes and/or ethene derivatives, formed from them via

• aryl hetaryl thioketones 1 (Table 1). As mentioned before, in some cases tri- and tetrasubstituted thiiranes partially underwent spontaneous extrusion of sulfur to form the corresponding tri- or tetrasubstituted ethene derivatives 9. In these cases, complete desulfurization was achieved by treatment of

• . Only after warming up above −45/40 °C compounds 2 are expected to decompose yielding the reactive thiocarbonyl ylide 3. Under these conditions, the latter intermediates can undergo either 1,3-dipolar electrocyclization to give thiiranes 8 or dimerization leading to 1,4-dithianes 4 [20][26]. This

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• =S ylides bearing at least one acyl group is identified as the 1,5-electrocyclization into 1,3-oxathioles. However, in the case of diazomalonates, the dominating process is 1,3-cyclization into thiiranes followed by their spontaneous desulfurization yielding the corresponding alkenes. Finally

• stage of the cycloaddition process. Keywords: diazocarbonyl compounds; 1,3-dipolar cycloaddition; 1,3-oxathioles; thiiranes; thiocarbonyl ylides; thioketones; Introduction Dipolar cycloadditions of diazo compounds have been of great interest for a long time as they provide a means for the preparation

• diazodiketones were essentially indifferent to aromatic and aliphatic thioketones under similar reaction conditions (Scheme 1) [14][15][19][20][21]. Generally, the main reaction products formed in these reactions were 1,3-oxathioles 3. However, in some cases, thiiranes 4 and alkenes 5 were isolated from the

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• -oxathiole to alkene were performed at the DFT PBE1PBE/6-31G(d) level. Keywords: 1,3-dipolar electrocyclization; 1,5-dipolar electrocyclization; 1,3-oxathioles; thiocarbonyl ylides; thiiranes; thioketones; Introduction Aryl- and alkylsubstituted thioketones exhibit high 1,3-dipolar reactivity towards

• [1][2][3][4] and easily eliminates N2 forming the reactive thiocarbonyl ylide 6. This intermediate, after subsequent 1,5- or 1,3-electrocyclization produces 1,3-oxathioles 3,7 or thiiranes 5 and 8, respectively (Scheme 2, path A) [4][5][6][22]. In some instances, substituted thiiranes undergo

• will lead to 1,3-oxathioles 3,7 or thiiranes/alkenes 5 and 8. It is known that reactions of diazo compounds with sterically demanding thioketones can give rise to fairly stable 1,3,4-thiadiazolines of type 10, that can be isolated and do not eliminate nitrogen up to 45 °C [4][23][24]. Hence, the

Imidazolinium and amidinium salts as Lewis acid organocatalysts

• Oksana Sereda,
• Nicole Clemens,
• Tatjana Heckel and
• René Wilhelm

Beilstein J. Org. Chem. 2012, 8, 1798–1803, doi:10.3762/bjoc.8.205

• and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause

• desulfurization of the products containing a thiol or thiocarbonyl group. Keywords: Diels–Alder; ionic liquids; organocatalysis; soft Lewis acids; thiiranes; thioesters; Introduction Salts with melting points below 100 °C are known as ionic liquids and are often used as novel solvents for reactions and

• time that these salts can interact with thiocarbonyl groups and thiiranes in order to activate these substrates. In addition, it was found that 7-membered 1,3-diazepinium cations are good catalysts for the ring opening of epoxides and that these salts are more reactive than imidazolinium salts. Diels

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• of ammonium acetate/sulfur/acidic alumina under solvent-free conditions using microwave irradiation. [49] This reagent can be used as an efficient reagent for the conversion of epoxides to thiiranes. This ambident nucleophile has two potentially attacking atoms (S or O) and can attack with either of