Ruzicka cyclization

This process, called Ruzicka cyclization, is good for the preparation of rings of six and seven members and, with lower yields, of Cg and Cio to C30 cyclic ketones. Not much work has been done on the mechanism of this reaction. However, a free-radical mechanism has been suggested on the basis of a thorough study of all the side products. ° ... 

This process, called Ruzicka cyclization, is good for the preparation of rings of 6 and 7 members and, with lower yields, of C8 and Ct0 to C30 cyclic ketones.1718... 

The Ruzicka Cyclization (or Ruzicka Large Ring Synthesis) is a similar reaction in which cyclic ketones are formed from salts (Ca or Ba for smaller rings and Th or Ce for larger rings) of diacids ... 

A simple efficient synthesis of the bicyclic enamine 31 (95%) by distillation of the ro-carboxyalkyllactam 145 from soda lime seems to be a variant of the classical Ruzicka cyclization of dicarboxylic acids (83CJC2016). 

Tissue cultures of Isodon japonicus could biosynthesize oleanane- and ursane-type triterpenoids from [4-13C]MVA with sufficient incorporation of tracer to allow the elucidation of the labelling pattern by 13C n.m.r. spectroscopy.356 The results verify the hypothesis of Ruzicka involving cyclization of 2,3-oxidosqualene in a chair-chair-boat form, followed by specific 1,2-hydride shifts, and the rearrangement of... 

Investigations with tissue cultures of Isodon japonicus using [l,2- C]acetate have been extended to the study of the formation of ring E of ursolic acid. Ruzicka s hypothesis for the cyclization of 2,3-oxidosqualene appears to hold for the ursanes (103) and (104) as indicated in Scheme 17, and routes involving the carbonium ion (105) can be excluded. 

This reaction was reported first by Ruzicka et al. in 1924 and was extended by Ainley and King in 1935. It is a multistep synthesis of a-piperidyl-4-quinolinemethanols (or quinolyl-4-a -piperidylcarbinols" ), involving the reaction of (a) amidation of p-anisidineby an acetoacetic ester, electrophilic cyclization to give 2-hydroxy-lepidine, (c) replacement... 

Compared to that of the Ruzicka protocol, the Claisen-Geuther ester condensation in this synthesis was optimized from 17% to 64% by replacement of sodium ethoxide with sodium or sodium amide. In addition, the cyclization to form the piperidinyl ring is carried out in a two-phase solvent system (H2O and ether) using sodium carbonate as base. ... 

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