Polylithiumorganic Compounds - 19.

Maercker, Adalbert; Daub, Volker E. E.

doi:10.1016/s0040-4020(01)86961-1

Cited by 19 publications

(11 citation statements)

References 45 publications

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“…Standard 1-D NMR, IR, and MS experiments were performed to identify the products from known spectra. The major product was cyclopropylidenecyclobutane ( 18 ) − followed by 1-methylenespiro[2.3]hexane ( 19 ). ,, Lesser amounts of bicyclo[3.2.0]hept-1(5)-ene ( 20 ) ,,− and 1,2-dimethylenecyclopentane ( 21 ) ,, were also formed. An unidentified hydrocarbon ( 22 ) was formed in trace amounts.…”

Section: Resultsmentioning

confidence: 99%

“…20% DC-200, 4.5 m, T oven = 100 °C, T TCD = 120 °C, T injector = 125 °C, carrier flow = 120 mL He/min; 98.7% purity; δ H /ppm (400.1 MHz, CDCl 3 ) 0.94–1.00 (4 H, quint, 5 J 2.5), 1.95–2.06 (2 H, quint, 3 J 8), 2.71–2.78 (4 H, tquint, 3 J 8, 5 J 2.5); , δ C /ppm (100.6 MHz, CDCl 3 ) 1.8 (2 × CH 2 ), 17.4 (CH 2 ), 31.1 (2 × CH 2 ), 109.8 (C), 128.4 (C); ν̅ /cm –1 (film) 3040, 2920, 2140, 2060, 2000, 1930, 1775, 1700, 1410, 1240, 1140, 1060, 1040, 965, 900, 870, 830, 760, 730, 705; , m / z (EI, 70 eV) 94 (M + , 22), 93 (18), 91 (20), 79 (100), 77 (48), 66 (30), 65 (24), 51 (11), 40 (11), 39 (36) …”

Section: Experimental Sectionmentioning

confidence: 99%

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Competitive 1,2-C Atom Shifts in the Strained Carbene Spiro[3.3]hept-1-ylidene Explained by Distinct Ring-Puckered Conformers

Rosenberg

Schrievers²,

Brinker

2016

J. Org. Chem.

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Spiro[3.3]hept-1-ylidene is a markedly strained carbene reaction intermediate that was generated by high-vacuum flash pyrolysis (HVFP) of the corresponding p-tosylhydrazone sodium salt. Five hydrocarbons were produced from the Bamford-Stevens reactant in 82% overall yield. The carbene undergoes two [1,2]-sigmatropic rearrangements via competing 1,2-C atom shifts. Ring-contraction yields cyclopropylidenecyclobutane, while ring-expansion affords bicyclo[3.2.0]hept-1(5)-ene. The ring contraction is regiospecific despite the formation of some 1-methylenespiro[2.3]hexane. It does not originate from the carbene under HVFP conditions. Instead, it comes from a methylenecyclopropane-type rearrangement of chemically activated cyclopropylidenecyclobutane. Similarly, some chemically activated bicyclo[3.2.0]hept-1(5)-ene rearranges to 1,2-dimethylenecyclopentane via electrocyclic ring-opening. Accounting for the conversion of primary products to secondary ones, relative yields indicate that ring-contraction within the carbene prevails over ring-expansion by a factor of 6.7:1. Computational chemistry was used to assess the structures, conformations, energies, strain energies, transition states, and activation energies of these rearrangements with the goal of explaining product selectivities. The dual-ringed carbene is predicted to assume four distinct geometric conformations that have a bearing on transition-state selection. The reactive cyclobutylidene units of two conformers are significantly puckered, like cyclobutylidene itself, while those of the other two are flatter. The selectivity of the title carbene is compared with that of spiro[2.3]hex-4-ylidene.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Competitive 1,2-C Atom Shifts in the Strained Carbene Spiro[3.3]hept-1-ylidene Explained by Distinct Ring-Puckered Conformers

Rosenberg

Schrievers²,

Brinker

2016

J. Org. Chem.

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“…Kinetically controlled 1,4-H and 1,6-D shifts of the vinylogous addition intermediate 9 , 18 dependent on the acidity of the proton adjacent to the carboxylate group, give 10 and 11 , respectively, and 10 is prone to deuteron-proton exchange (from 10 to 12 ) with further loss occurring during cyclization and aromatization.…”

Section: Resultsmentioning

confidence: 99%

Vinylogous Reactivity of Enol Diazoacetates with Donor–Acceptor Substituted Hydrazones. Synthesis of Substituted Pyrazole Derivatives

Zavalij

et al. 2013

J. Org. Chem.

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“…Compound 7 was purchased from commercial sources; compound 12 (ref. 21) and cyclopropyltriphenylphosphonium bromide 22 were prepared using the procedures reported in the literature. Melting points were measured on an automated melting point system.…”

Section: Generalmentioning

confidence: 99%

Conformationally restricted glutamic acid analogues: stereoisomers of 1-aminospiro[3.3]heptane-1,6-dicarboxylic acid

et al. 2014

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Polylithiumorganic Compounds - 19.

Cited by 19 publications

References 45 publications

Competitive 1,2-C Atom Shifts in the Strained Carbene Spiro[3.3]hept-1-ylidene Explained by Distinct Ring-Puckered Conformers

Competitive 1,2-C Atom Shifts in the Strained Carbene Spiro[3.3]hept-1-ylidene Explained by Distinct Ring-Puckered Conformers

Vinylogous Reactivity of Enol Diazoacetates with Donor–Acceptor Substituted Hydrazones. Synthesis of Substituted Pyrazole Derivatives

Conformationally restricted glutamic acid analogues: stereoisomers of 1-aminospiro[3.3]heptane-1,6-dicarboxylic acid

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