Rearrangement ring expansion

The Pd(0)-catalyzed rearrangement of the iV-allylenamine 800 in CF3CO2H affords the (5, -unsaturated imine 801, which is hydrolyzed to give the 7, 8-unsaturated aldehyde 802[498]. The vinyloxaspirohexane 803 undergoes rearrangement-ring expansion to give the cyclopentanone 804 in the presence of 1 equiv. of p-nitrophenol[499]. 

W-M rearrangement ring expansion at expense of tertiary—> secondary cation... 

Most such heterobicyclic substrates are fused pyrazines from which the second ring must be removed completely or in part by oxidation, hydrolysis, or some other means to afford the desired monocyclic pyrazine derivatives. However, some such bicyclic substrates do not already incorporate a pyrazine ring, so that more profound processes (like rearrangement, ring expansion, or use of a cosynthon) must be employed to furnish pyrazines. 

Addition of acetylenic esters to cyclic enamines leading by rearrangement ring expansion to cyclic ketones with two more carbon atoms. 

MORIN Penicillin Rearrangement Ring expansion of penams to cephems under acidic catalysis. 

With a variety of catalyzed and uncatalyzed reaction conditions for the Michael addition and aza-Claisen rearrangement, ring expansion was explored by reacting the five- and six-membered amines (31) and (32) with dimethyl acetylenedicarboxylate (DMAD), as the Michael acceptor <94JA579> (Equations (5) and (6)). The cyclic enamines are rather sensitive to hydrolysis during... 

Sulfuric acid acetic acid Beckmann rearrangement Ring expansion... 

Similar carbopalladation-ring expansion was observed in the Pd-catalyzed reaction of the (hydroxy)- methoxyallenylisoindoline bearing an iodophenyl moiety 59. In this case, carbopalladation of the allene to form the r-allylpalladium is followed by rearrangement-ring expansion, as shown by 60, to give the isoquinolinedione... 

The allenyl alcohol without the iodophenyl moiety 62 alone undergoes the Pd-catalyzed rearrangement-ring expansion to give the isoquinolinedione 63 [11]. 

Lessard, Spino, and coworkers developed the formation of iV-heterocycles from cycloalkanones using a photochemical ring contraction reaction coupled with a Beckmann rearrangement ring expansion." Their methodology is an impressive approach to transform disubstituted cycloalkanones into N-heterocycles of the same ring size tSchemp The... 

Complementary to the hetero-Pauson-Khand reaction (see Section 2.2.6), [2 + 2] cydoaddition of ketenes and aldehydes provides rapid access to P-lactones from relatively simple starting materials. Cationic [Pd(dppb)(CH3CN)2]Bp4 was selected as the optimal catalyst (Scheme 2.64) (122,123]. A tandem allylic rearrangement/ring expansion sequence was also developed that provides elaboration of P-lactones to 3,6-dihydro-2H-pyran-2-ones in a one-pot process (Scheme 2.65) [123]. 

Poly phosphoric acid sodium azide Lactams from cyclic ketones by Schmidt reaction and from cyclic oximes by Beckmann rearrangement Ring expansion... 

Media s. Solvents Medium, superacidic reactions in - 27,159 Meerwein s. Wagner Meisenheimer rearrangement, ring expansion by - 26, 151 Meldmn s acids s. Malonic acid esters, cyclic Mercaptals... 

SCHEME 17.13. Enantioselective synthesis of (—)-indolizidines 209B 57 and 209D 58 by an aza-[2,3]-Wittig rearrangement ring expansion of aziridine 55. 

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