Variable-temperature NMR and X-ray crystallographic studies of 5-dimethylaminomethylene-, 5-dimethylaminopropenylidene-, and 5-(5-dimethylaminopenta-2,4-dienylidene)-derivatives of Meldrum's acid and related dimethyl malonate derivatives

Blake, Alexander J.; McNab, Hamish; Monahan, L. C.

doi:10.1039/p29910002003

Cited by 15 publications

(11 citation statements)

References 8 publications

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“…There is an indication, at the limits of precision, that delocalization of the N-atom lone pair into the Meldrum's acid ring may be favoured in the direction of one of the two carbonyl groups. The structure is otherwise very similar to that of previously reported 2,2-dimethyl-5-(N,N-dimethylaminomethylene)-1,3-dioxane-4,6-dione [Blake et al (1991). J.…”

supporting

confidence: 86%

“…Thus C4ÐC5 [1.437 (4) A Ê ] displays more doublebond character than C5ÐC6 [1.452 (4) A Ê ] and C4ÐO4 [1.218 (3) A Ê ] correspondingly displays more single-bond character than C6ÐO6 [1.208 (3) A Ê ]. Although this feature was not observed in the structure of (2), we have previously made a similar observation in the structure of the vinylogue (3) (Blake et al, 1991). Interestingly, in this case, the preferred delocalization took place towards the other carbonyl group.…”

Section: Commentsupporting

confidence: 70%

“…The dihedral angle between the C4/C5/C6 and the C7/N8/C9 planes is 26.0 (6) . By comparison with its N,N-dimethyl analogue, (2) (Blake et al, 1991), the methoxy group has comparatively little structural in¯uence on the molecule as a whole. Thus, many of the values of the corresponding bond lengths and valence angles in (1) and (2) (including C5ÐC7 and C7ÐN8) lie within one s.u.…”

Section: Commentmentioning

confidence: 99%

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2,2-Dimethyl-5-(N-methyl-N-methoxyaminomethylene)-1,3-dioxane-4,6-dione

2003

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confidence: 86%

Section: Commentsupporting

confidence: 70%

Section: Commentmentioning

confidence: 99%

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2,2-Dimethyl-5-(N-methyl-N-methoxyaminomethylene)-1,3-dioxane-4,6-dione

2003

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“…The BLA value of linear DASAs with dialkyl‐substituted electron‐donating part is larger than those with aryl‐substituted electron‐donating part (Figure 3). [ 23‐25 ] It is worth noting that the zwitterionic resonance structure in crystal is dominated with strong BLA.…”

Section: Chemistry Of Sps and Dasasmentioning

confidence: 99%

Learning from Spiropyrans: How to Make Further Developments of Donor‐Acceptor Stenhouse Adducts

et al. 2021

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Photoresponsive| Donor-acceptor Stenhouse adducts| Spiropyrans| Applications| Isomerization Donor-acceptor Stenhouse adducts (DASAs) as a species of novel photochromic molecules, have been developing rapidly and attracting broad researchers' sights since 2014. DASAs show visible/near-infrared (NIR) light induced linear-to-cyclic isomerization and heat induced cyclic-to-linear isomerization, therefore they are attractive in photoresponsive hydrogels, drug delivery, cell culturing and tissue engineering. As a series of well-known photoresponsive molecules, spiropyrans (SPs) show similar molecular properties and comparable photoswitching with DASAs. UV light triggers closed-to-open (also known as spirocyclic (SC)-to-merocyanine (MC)) isomerization of SPs, while the reversed open-to-closed isomerization occurs under visible light or heat. Light irradiation switches the molecular color, scale, geometry, and polarity of SPs and DASAs reversibly. Since the researches on DASAs are still in the infancy, the chemical structures, isomerization mechanisms and potential applications need to be further investigated and explored. The well-studied SPs have important reference values to the comprehensive developments of DASAs. In the present review, we summarized, compared and discussed SPs and DASAs with regards to their molecular structures, synthesis, photoswitching and applications. We also make our perspective on the developments of DASA in future. Yongli Duan (lest) is a Ph.D. student at University of Electronic Science and Technology of China. She is focusing on the synthesis, photoresponsive mechanisms and properties of DASAs under supervision of Prof. Dr. Dongsheng Wang.

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“…In some examples this peak is broad, indicating that exchange processes may be operating such as those found in dialkylaminomethylidene Meldrum's acid derivatives. 17 Flash vacuum pyrolysis of the Meldrum's acid derivatives 10-15 and 18 at ca. 600 ЊC (10 Ϫ2 -10 Ϫ3 Torr) gave the pyrrolizin-3-ones 19-25 in excellent yield (typically 70-90%) and in high purity (Scheme 2).…”

mentioning

confidence: 99%

Synthesis of pyrrolizin-3-ones by flash vacuum pyrolysis of pyrrol-2-ylmethylidene Meldrum’s acid derivatives and 3-(pyrrol-2-yl)propenoic esters

Campbell¹,

Comer²,

Derbyshire³

et al. 1997

J. Chem. Soc., Perkin Trans. 1

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Monosubstituted pyrrolizin-3-ones 1 with substituents at the 1-, 5-, 6-or 7-positions are prepared in excellent yield by flash vacuum pyrolysis (FVP) of appropriate Meldrum's acid derivatives 2. The mechanism involves formation of the pyrrol-2-ylmethylideneketene 29, which can also be generated thermally from 3-(pyrrol-2-yl)propenoate esters (e.g. 30). This alternative route has been used to make a range of 2-substituted pyrrolizin-3-ones, again in excellent yield. The 3-oxo-3H-pyrrolizine-2-carboxylic acid 42 could not be made in this way owing to facile decarboxylation to pyrrolizinone 1, and extension to the formation of the azaazulenone 48 was again unsuccessful.Some years ago we reported a simple and efficient synthesis of pyrrolizin-3-one 1 by flash vacuum pyrolysis (FVP) of the condensation product 2 of pyrrole-2-carbaldehyde and Meldrum's acid. 1 Later, we applied this methodology to the crystalline 6-bromo derivative 3, 2 and obtained the first X-ray crystallographic data for this ring system. 2 The Meldrum's acid route was also used to make certain azapyrrolizinone ring systems for the first time, 3 and their NMR spectra have been discussed in detail. 4 Since pyrrolizinones remain relatively unexplored in the literature, 5 we now report a more extensive study of the scope and mechanism of this synthetic route from which a complementary pyrolytic synthesis via pyrrolylpropenoic esters has evolved. 6 Our corresponding work on the azapyrrolizinones is discussed in the accompanying paper. 7Two routes to the key Meldrum's acid precursors were employed (Scheme 1). The classic Knoevenagel condensation N R 6 O O O O O N H 3 R 6 = Br 1 R 6 = H 2 Scheme 1 Reagents and conditions: i, piperidinium acetate, toluene, 20 ЊC; ii, acetonitrile, 20 ЊC O O O O N H R O O O O O O O O OMe N H R N H CHO ii i Route b Route a + + 4 Rusing piperidinium acetate catalyst 8 in toluene at room temperature (Scheme 1, route a) works well if the appropriate pyrrole-2-carbaldehyde is readily available. Thus, we have used the photochemical ring contraction of 4-substituted pyridine N-oxides 9-11 to prepare a range of 3-substituted pyrrole-2-carbaldehydes 5-7 containing electron donating and electron withdrawing groups, and we prepared ethyl 5-formylpyrrole-2-carboxylate 8 by Vilsmeier formylation of the ester using a literature method. 12 Yields for the Meldrum's acid condensation to give the derivatives 10-13 were in the range 62-98%. Condensation of Meldrum's acid with 2-acetylpyrrole 9 was achieved by the titanium tetrachloride method 13 though the yield of 18 obtained in this way was consistently lower than for the aldehyde reactions (57%). We have also reported a direct route to 2 by reaction of N H CHO R 3 N H CHO EtO 2 C N H Me O O O O O O O O O N H Me 9 8 5 R 3 = Me 6 R 3 = OMe 7 R 3 = CO 2 Me N R 4 R 3 R 5 H 18 10 R 3 = Me, R 4 = R 5 = H 11 R 3 = OMe, R 4 = R 5 = H 12 R 3 = CO 2 Me, R 4 = R 5 = H 13 R 3 = R 4 = H, R 5 = CO 2 Et 14 R 3 = R 4 = H, R 5 = Me 15 R 3 = R 4 = H, R 5 = Ph 16 R 3 = Ph, R 4 = R 5 = H 17 R 3 = R 5 = H, R 4...

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Variable-temperature NMR and X-ray crystallographic studies of 5-dimethylaminomethylene-, 5-dimethylaminopropenylidene-, and 5-(5-dimethylaminopenta-2,4-dienylidene)-derivatives of Meldrum's acid and related dimethyl malonate derivatives

Cited by 15 publications

References 8 publications

2,2-Dimethyl-5-(N-methyl-N-methoxyaminomethylene)-1,3-dioxane-4,6-dione

2,2-Dimethyl-5-(N-methyl-N-methoxyaminomethylene)-1,3-dioxane-4,6-dione

Learning from Spiropyrans: How to Make Further Developments of Donor‐Acceptor Stenhouse Adducts

Synthesis of pyrrolizin-3-ones by flash vacuum pyrolysis of pyrrol-2-ylmethylidene Meldrum’s acid derivatives and 3-(pyrrol-2-yl)propenoic esters

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