Flash thermolysis of spiro[2,3]hexan-4-ones. A case of vinylketen generation

Rousseau, G.; Bloch, Robert J.; Perchec, P. Le; Conia, J. M.

doi:10.1039/c3973000795b

Cited by 14 publications

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“…Found: C, 80.30; H, (E)-7-Ethylidenebicyclo[3.2.0]hept-2-en-6-one (3). The fourth-eluting component, which constituted 63.29% of the mixture, was assigned structure 3: mass spectrum m/e (rel intensity) 134 (28), 106 (11), 105 (12), 91 (35), 78 (10), 69 (9), 68 (9), 67 (8), 66 (100), 65 (11), 51 (10), 41 (13), 40 (16), 39 (23); ir 3030, 2930, 2860,1745,1668, 1605,1442,1171,1075, 793, 735, 690 cm"1; NMR (0.0395 g in 350 µ of CDC13) 6.23, q (J = 7 Hz) further split into a doublet (J = 1.0 Hz), 1 H (Hg); 5.8, m, 2 H (H2, H3); 3.7, m, 2 H; 2.6, m, 2 ; 1.81, d of d (J = 7,1.0 Hz), 3 H (CH3). LIS NMR: sequential addition of a CDC13 solution of Eu(fod)339 and spectral measurements were made as de-J.…”

Section: Methodsmentioning

confidence: 99%

Preparation of vinylketene by 1,4-elimination. Cycloaddition and isomerization to form .alpha.-ethylidenecyclobutanones

Holder¹,

Freiman²,

STEFANCHIK³

1976

J. Org. Chem.

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Vinylketene (1) was shown to result from triethylamine initiated 1,4-dehydrochlorination of trans-2-butenoyl chloride. In the presence of 1,3-cyclopentadiene a ,2 + T2 cycloaddition occurred to form adduct 2. With a trace of excess triethylamine 2 isomerized chiefly to a 73:27 mixture of the E and Z isomers 3 and 4, whose structures were securely assigned using lanthanide induced shift nuclear magnetic resonance techniques. The possible participation of ethylideneketene (CHaCH=C=C=0) was judged remote since triethylamine, 3-butenoyl chloride, and 1,3-cyclopentadiene gave an identical reaction mixture. With either isomeric acid chloride if less than 1.0 molar equiv of triethylamine was used a 60:01:39 mixture of 2:3:4 was formed, which upon addition of triethylamine equilibrated to the 73:27 mixture of 3 and 4. Ketenes (RR'C=C=0) react with conjugated dienes in a highly perispecific and regiospecific manner to form 3-• vinylcyclobutanones.4 Since the olefinic component reacts suprafacially, the fusion geometry is consistently cis. When the two ketene substituents differ in steric bulk the larger one tends to assume the more hindered position in the product.5,6 Ketene cycloadditions represent one of the few synthetic approaches to four-membered rings,7 and also serve as sensitive mechanistic probes of the rare and difficult T2S + T2a allowed concerted8 pathway. A review of the available evi-dence4 and recent theoretical analyses9,10 indicate that both concerted and nonconcerted routes may be traversed, depending on the steric and electronic characteristics of ketene and ketenophile.

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Section: Methodsmentioning

confidence: 99%

Preparation of vinylketene by 1,4-elimination. Cycloaddition and isomerization to form .alpha.-ethylidenecyclobutanones

Holder¹,

Freiman²,

STEFANCHIK³

1976

J. Org. Chem.

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“…The synthetic strategy I involves the formation of 2,3-diaryl-4-methylenecyclobutene-1-chalcogenones C and the subsequent intramolecular oxidative biaryl coupling to form phenanthrocyclobutenone derivatives D prior to the hetero Diels-Alder reaction of in situ generated α-allenylchalcogenolketenes B with cyclic imines E, [46][47][48] and both synthetic strategies II and III involve hetero Diels-Alder reaction of in situ generated α-allenylchalco-genoketenes B with cyclic imines E forming indolizidine core. In strategy II, the subsequent intramolecular oxidative biaryl coupling of synthetic intermediates G, [49][50][51][52][53][54][55] structurally related to some unfused quinolizidine alkaloids as septicines, [56][57][58][59] is required, and synthetic strategy III requires the hetero Diels-Alder reaction of alkynyl propargyl chalcogenides A bearing a functionalized biphenyl moiety at the R 2 substituent in advance in order to achieve the subsequent photochemical ring closure to form phenanthroindolizidine core I.…”

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confidence: 99%