Sulfur Ylides. Part 13. Synthesis and Intramolecular Cyclization of Keto‐Stabilized Sulfur Ylides.

Галин, Ф. З.; Sakhautdinov, I. M.; Lakeev, S. N.; Егоров, В. А.; Фатыхов, А. А.; Maidanova, I. O.

doi:10.1002/chin.200644122

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“…The mass spectra (atmospheric pressure chemical ionization) were obtained on a Shimadzu LCMS-2010EV instrument. Microwave-assisted reactions were carried out in a 50-ml quartz reactor placed in a modified multimode cavity based on a SAM-OM75S-(31) magnetron (2.45 × 10 9 Hz, 750 W); the mechanical stirrer drive unit and reflux condenser were mounted outside the microwave radiation zone. Ultrasound was generated using a UZDN-2T setup with an operating frequency of 22 kHz.…”

Section: Methodsmentioning

confidence: 99%

“…According to published data [5][6][7][8][9][10][11][12] and NMR spectra, protons at the double bonds (δ 6.42 ppm) appear in the vicinity of the phthalimide fragments, and protons in the cyclobutane ring (δ 4.43 ppm) are located in the α-positions with respect to the ester groups and are oriented cis with respect to each other, as follows from their equivalence due to molecular symmetry.…”

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“…Signals from the methylene and olefinic protons appeared in the 1 H NMR spectra as singlets. The upfield position of the CH 2 signal of VII (δ 3.51 ppm) as compared to VIII (δ 5.21 ppm) suggests that the methylene group in VII is neighboring to the ester fragment rather than phthalimide as in VIII [5][6][7][8][9][10][11]. The symmetric structure of VII is also confirmed by the presence of only one cross peak in the 1 H-15 N HMBC spectrum (δ/δ N 6.48/165), as well as by correlations of the olefinic proton with the carbonyl carbon atom in the phthalimide fragment (δ/δ C 6.48/165.47 ppm), quaternary carbon atom at the double bond (δ C 117.98 ppm), and methylene carbon atom (δ C 42.53 ppm).…”

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Thermal oligomerization of methyl 4-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)buta-2,3-dienoate

et al. 2012

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Dimeric compounds formed as a result of thermal oligomerization of methyl 4-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)buta-2,3-dienoate were identified.Cyclobutane derivatives attract increased attention of many researchers. This is related to both specific structure and chemical properties of compounds containing a cyclobutane ring and their possible application in medicine, primarily as antiviral and antitumor drugs [1,2]. Interest in such structures stimulates development of simple, inexpensive, and general procedures for their preparation with a view to obtain new derivatives, taking into account that the number of available cyclobutane compounds is not large. Substituted allenes were shown [3] to be promising as starting compounds for the synthesis of cyclobutane derivatives [3].In the present work we studied transformations of allene II having a phthalimide fragment, which was synthesized by the Wittig reaction of N-phthaloylglycine (I) prepared in turn by direct fusion of phthalic anhydride with glycine (Scheme 1). The Wittig reaction of I afforded 63% of allene II and 5% of ylide III. The structure of the products was proved by spectral data. The 1 H NMR spectrum of II contained doublet signals at δ 6.21 and 7.25 ppm due to protons in the allene fragment, and the allene carbon atoms gave signals at δ C 91.75, 96.66 (-CH=), and 209.97 ppm (=C=) in the 13 C NMR spectrum.It is known that thermal activation of allene leads to its dimerization [3,4]. Heating of allene II in boiling toluene under microwave irradiation and without it, as well as under polymerization conditions in the presence of azobis(isobutyronitrile) (AIBN) and in the absence of initiator, gave substituted cyclobutanes IV-VI (Scheme 2). Joint oligomerization of allenes with unsaturated compounds is known to produce methylenecyclobutane and methylenecyclobutene derivatives [3,4]. In our case, the reaction of allene II with dimethyl acetylenedicarboxylate resulted in dimerization of the allene rather than in co-oligomerization (see table). The structure of the dimeric products was determined by IR and NMR spectroscopy, mass spectrometry, and elemental analysis.The 1 H NMR spectra of IV and V contained two three-proton singlets from methyl protons in the two nonequivalent ester groups at δ 3.29, 3.79 and 3.37, 3.76 ppm, respectively, which indicated formation of

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Section: Methodsmentioning

confidence: 99%

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