Lewis acid-promoted hetero Diels–Alder reaction of α,β-unsaturated thioketones

Motoki, Shinichi; Saito, Takao; Karakasa, Takayuki; Matsushita, T.; Furuno, E.

doi:10.1039/p19920002943

Cited by 26 publications

(14 citation statements)

References 18 publications

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“…Moreover, the coupling constants J = 4.2-4.4 Hz between the axial HC(3) and the equatorial HC(4) observed for the series 4 j-l strongly support the structure of endo-cycloadducts (Scheme 3). [13] Notably, also in the case of the a-d series only endo-dimers 4 could be identified in the mixtures.…”

Section: Synthesis Of Thiochalcones and Dimerizationmentioning

confidence: 93%

“…Noteworthy, thiochalcones 1 exist in solutions as equilibrium mixtures of monomeric and dimeric forms, namely 3,4-dihydro-1,2-dithiin 2 and 3,4-dihydro-2H-thiopyran derivatives 4 (Scheme 2). [13] The dimeric products are formed through thia-Diels-Alder reactions with thiochalcones playing at the same time the role of the heterodiene and the C=S dienophile (!1,2-dithiins 2 or 1,3-dithiins 3) or C=C dienophile (!thiopyrans 4 or 5). Surprisingly, in contrast to several a,b-unsaturated thioaldehydes such as thioacrolein, there is no indication that thiochalcones 1 provide the regioisomeric dimers 3 (1,3-dithiins) or the regioisomeric 3,4-dihydro-2H-thiopyran 5.…”

Section: Introductionmentioning

confidence: 99%

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The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

Mlostoń

Urbaniak

Jasiński

et al. 2019

Chemistry A European J

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The [4+2]‐cycloadditions of α‐nitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styryl‐substituted 4H‐1,5,2‐oxathiazines in moderate to good yields. Of the eight conceivable hetero‐Diels–Alder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the α‐nitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bis‐heterocyclic [4+2]‐cycloadducts. The experiments are supported by high‐level DFT calculations that were also extended to related hetero‐Diels–Alder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2‐dithiin and 2H‐thiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process.

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Section: Synthesis Of Thiochalcones and Dimerizationmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

Mlostoń

Urbaniak

Jasiński

et al. 2019

Chemistry A European J

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“…Their 1 H NMR spectra are fairly complex but nevertheless allow an unambiguous assessment of the constitution of the newly-formed 3,4-dihydro-2H-thiopyran rings. We begin with the signal at d = 3.0 ppm whose assignment to H4 follows known precedence [33][34][35][36][37] and is further supported by the observation, in the H,H-COSY spectra, of weak crosspeaks with the signals of the aryl group R 1 . H4 is coupled to three vicinal protons, establishing the regioselectivity of the cycloaddition as shown in Table 1.…”

Section: X-ray Structure Determinations Of [Cprua C H T U N G T R E Nmentioning

confidence: 99%

“…[33,34,43] The assignment of the 1 H NMR spectrum of the methylvinylketone adduct 14 d may serve as an example. In the major isomer, the CH 2 group next to sulfur shows the expected large geminal coupling and a large vicinal coupling to H3, which establishes an axial position for the latter.…”

Section: A C H T U N G T R E N N U N G [4+2]-cycloaddition Reactions mentioning

confidence: 99%

Ruthenium Complexes of Thiocinnamaldehydes: Synthesis, Structure, and [4+2]‐Cycloaddition Reactions

Schenk

Beucke

Burzlaff

et al. 2006

Chemistry A European J

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Ruthenium hydrogensulfido complexes [CpRu(P-P)(SH)] ((P-P)=Ph(2)PCH(2)PPh(2) (dppm), Ph(2)PC(2)H(4)PPh(2) (dppe)) were obtained from the corresponding chloro complexes by Cl/SH exchange. Condensation with a range of cinnamaldehydes gave thiocinnamaldehyde complexes [CpRu(P-P)(S=CH-CR(2)=CHR(1))]PF(6) (R(1)=C(6)H(4)X, R(2)=H, Me, X=H, OMe, NMe(2), Cl, NO(2)) as highly-colored crystalline compounds. The thiocinnamaldehyde complexes undergo [4+2]-cycloaddition reactions with vinyl ethers CH(2)=CHOR(3) (R(3)=Et, Bu) and styrenes H(2)C=CHC(6)H(4)Y (Y=H, Me, OMe, Cl, Br, NO(2)) to give complexes of 2,4,5-trisubstituted 3,4-dihydro-2H-thiopyrans as mixtures of two diastereoisomers. The rate of addition of para-substituted styrenes H(2)C=CHC(6)H(4)Y to [CpRu(dppm)(S=CH-CH=CHPh)]PF(6) increases in the series Y=NO(2), Br, Cl, H, Me, OMe, indicating that the cycloaddition is dominated by the HOMO(dienophile)-LUMO(diene) interaction. The strained dienophiles norbornadiene and norbornene also add, giving ruthenium complexes of 3-thia-tricyclo[6.2.1.0(2,7)]undeca-4,9-dienes and 3-thia-tricyclo[6.2.1.0(2,7)]undec-4-enes, respectively. Addition reactions with acrolein, methacrolein, methyl vinyl ketone, acrylic ester, or ethyl propiolate finally yielded ruthenium complexes of 3,4-disubstituted 3,4-dihydro-2H-thiopyrans and 4H-thiopyrans, respectively.

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“…[32][33][34][35] Therefore BF 3 etherate as well as ZnCl 2 were utilized as Lewis acids with a amount of 0.5 eq per functional unit thioamide. Addition of BF 3 resulted immediately in a brown precipitation and further degradation.…”

Section: Synthesis and Characterization Of 3b5 And The Oligomeric Spementioning

confidence: 99%

Reversible oligomerization of 3-aryl-2-cyanothioacrylamides via [2_s + 4_s] cycloaddition to substituted 3,4-dihydro-2H-thiopyrans

Kötteritzsch

Bode

Yildirim

et al. 2015

Designed Monomers and Polymers

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(2015) Novel difunctional monomers are synthesized which are able to dimerize as well as oligomerize via the hetero-DielsAlder (HDA) mechanism. These monomers are based on 3-aryl-2-cyanothioacrylamides, which are used as functional units for the HDA reaction to form 3,4-dihydro-2H-thiopyrans. Different substituents of the aromatic ring are utilized to shift the equilibrium to the dimeric or oligomeric species. The HDA reaction is reversible and can be influenced by the temperature as well as the concentration. In contrast, the N,N-dimethylthioacrylamide analogues do not dimerize or the dimerization is not reversible. The most promising compound is furthermore investigated in detail by 1 H NMR spectroscopy to elucidate the dimerization kinetics. In addition, a difunctional molecule is able to oligomerize reversibly, as confirmed by means of 1 H NMR, size exclusion chromatography (SEC), and ESI MS measurements. A respective alcohol is employed as initiator for the ring-opening polymerization of L-lactide resulting in an end-functional polymer that undergoes reversible dimerization as confirmed by SEC measurements.

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Lewis acid-promoted hetero Diels–Alder reaction of α,β-unsaturated thioketones

Cited by 26 publications

References 18 publications

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

Ruthenium Complexes of Thiocinnamaldehydes: Synthesis, Structure, and [4+2]‐Cycloaddition Reactions

Reversible oligomerization of 3-aryl-2-cyanothioacrylamides via [2_s + 4_s] cycloaddition to substituted 3,4-dihydro-2H-thiopyrans

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Lewis acid-promoted hetero Diels–Alder reaction of α,β-unsaturated thioketones

Cited by 26 publications

References 18 publications

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

Ruthenium Complexes of Thiocinnamaldehydes: Synthesis, Structure, and [4+2]‐Cycloaddition Reactions

Reversible oligomerization of 3-aryl-2-cyanothioacrylamides via [2s + 4s] cycloaddition to substituted 3,4-dihydro-2H-thiopyrans

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Reversible oligomerization of 3-aryl-2-cyanothioacrylamides via [2_s + 4_s] cycloaddition to substituted 3,4-dihydro-2H-thiopyrans