Ketenes diaryl

Michael addition in the absence of any catalytic agent has been reported for dialkyl and diaryl phosphites and thiophosphites with a-cyanoacrylate esters and a-cyanoacrylic acid.444 Yields of the conjugate addition products were moderate to good. The regiochemistry of this process is the opposite of that previously reported for similar additions to ketene acetals, the latter presumably proceeding by initial protonation of the distal olefinic carbon site.445... 

Highly enantioselective Mannich-type reactions of A-(2-hydroxyphenyl) aldi-mines with ketene trimethylsilyl acetals and of A-Boc-aldimines with acetyl acetone or furan are catalyzed by chiral phosphonic acids 9 derived from 3,3 -diaryl-(l )-BlNOL and POCI3 (Scheme 12.7). ... 

Benzyliden-amino)-l, 3,4-oxadiazole reagieren als Azadiene mit Diphenyl-keten unter Cycloaddition zu 2,7-Diaryl-6,6-diphenyl-5-oxo-6,7-dihydro-5H-685 ... 

Calculations of the interactions between matured catalytic antibody AZ28 and the different conformers and enantiomers of 2,5-diaryl-hexa-l,5-dien-3-ol, allowing for the flexibility of the antibody, have reproduced, qualitatively only, the observed selectivity of the antibody for the S,equatorial substrate.7 Doubly a,/9-unsaturated A-arylimines (3) have been shown to react with a,j3-unsaturated ketenes to give azocinones (4),... 

Polycyclic aromatic compounds are obtained upon irradiation of diaryl-substitnted chromium carbenes under a carbon monoxide atmosphere. The reaction probably proceeds via the formation of a biaryl-aUcoxy ketene followed by cyclization. For example, the pyrrole-substituted carbene (22) gave the tricyclic compound (23) (Scheme 34) Related intramolecular Friedel-Crafts-type reactions of carbenes having tethered electron-rich aromatic rings are feasible, usually in moderate yields (Scheme 35). A Lewis acid catalyst such as zinc dichloride is required for optimum yields. 

Bis-[hexafluor-isopropyliden]- 1,3-diaryl- E16c, 996 (aus Keten-imin)... 

Deoxygenation of a-diketones can be effected by triethyl phosphite to furnish acetylenes and triethyl phosphate (equation 103). Either one equivalent of the a-diketone is treated with 2 equivalents of trielhyl phosphite at 215 °C to furnish diaryl- or alkylarylacetylenes in 24-60% yields, or the 1 1 adducts 33 of the a-diketones and (EtO)3P are treated with excess reagent at 215 °C to afford the above acetylenes in 54-81% yields . The reaction apparently involves a disubstituted ketene, since diphenylketene gives with (EtO)3P a 1 1 adduct which on pyrolysis furnishes diphenylacetylcne in 40% yield (equation 103) . Several diacetylenes of types 34 and 35 have been prepared in this manner . ... 

The most important method for the preparation of aryl ketones is known as Friedel-Crafts acylation. The reaction is of wide scope. Reagents other than acyl halides can be used," including carboxylic acids," anhydrides, and ketenes. Oxalyl chloride has been used to give diaryl 1,2-diketones." Carboxylic esters usually give alkylation as the predominant product (see 11-11)." A-Carbamoyl p-lactams reacted with naphthalene in the presence of trifluoromethanesulfonic acid to give the keto-amide." ... 

Pentenenitriles and benzo[f]indoles. Ally iminophosphoranes are formed from the corresponding azides upon treatment with PPh j (Staudinger reaction). Condensation of these products with diaryl ketenes leads to 4-pentenenitriles by a sig-matropic rearrangement. In the homoallyl series the Wittig reaction is followed by an intramolecular Diels-Alder reaction. Mild dehydrogenation of the products gives ben zo[/] indoles. ... 

The synthesis of pm-substituted 3,4-diaryl-thienothiophene 120 from (4-MeC6H4CH2)2CO through the corresponding ketene dithioacetal, Dieckmann cyclization, hydrolysis and decarboxylation was described (2000SC1695). 

The condensation of (chlorocarbonyl)phenylketene or (chlorocarbonyl) benzylketene with 1,3-dinucleophiles such as N-phenylthiocarbamates 520a and N-phenylcarbamates 520b resulted in the generation of relatively unstable mesoionic 1,3-thiazinium 4-olates I or 1,3-oxazinium 4-olates II which can be transformed into 3,5-diaryl l,3-thiazine-2,4,6-triones 521 and alkoxy-3,5-diphenyl-3H-l,3-oxazine-2,6-diones 522 (Scheme 172). In accordance with proposed mechanism, the nitrogen atom of 520 attacks the central carbon atom of the ketene group, with a low-lying LUMO,... 

Addition of keten to 3-dialkylaminovinylthiones provides a route to 4,6-diaryl- or 6-aryl-2H-thiopyran-2-ones, whilst 5,6-diaryl-3-cyano-derivatives can be prepared from (3-mercapto- or 3-chloro-acroleins (22 R = SH or Cl). Full details have been published of the formation of 2H-thiopyran-2-thiones in condensation reactions between 1,2-dithiolium salts and aroyldithioacetic esters. ... 

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