Transposition double

This reaction has been indepoidently reinvestigated by Lauer and Schmid. Rearrangement of (1), bearing a C label at the distal carbon of the allylic moiety (starred), gives phenol (4) with 84% of the label at the terminal carbon of the side chain and 16% at the methylene group. This result demonstrates that the reaction proceeds principally through a double transposition of the allylic residue the labeling pattern is maintained independent of the pathway to phenol (4). 

This group consists of the identity element 1, the double transpositions (01)(23), (02)(13), (03)(12), the eight 3-cycles, namely (012), (013), (023), (123) and their inverses. Or, in terms of the sign of permutations, the alternating group A4 consists of the permutations for which... 

The double bond transposition could also be achieved by the conversion of an intermediate for PGA2 synthesis into a 1,3-diene iron tricarbonyl complex from which PGC2 was synthesized in four steps. The Fe(CO)3 diene complex which survived the Wittig reaction was cleanly removed by Collins reagent in the subsequent step (Ref. 10). 

The overall reaction includes allylic transposition of a double bond, migration of the allylic hydrogen and formation of a bond between ene and enophile. Experimental findings suggest a concerted mechanism. Alternatively a diradical species 4 might be formed as intermediate however such a species should also give rise to formation of a cyclobutane derivative 5 as a side-product. If such a by-product is not observed, one might exclude the diradical pathway ... 

Umsetzung, /. transposition double decomposition conversion, change transformation reversal reaction transplantation exchange, sale, business. Umsetzungsgeschwindigkeit, /. velocity of transformation, reaction rate. 

Use of Lewis acid catalysts allows allylic stannanes to react under mild conditions. As is the case with allylic silanes, a double-bond transposition occurs in conjunction with destannylation.159... 

In many allylic oxidations, the double bond is found in a position indicating that an allylic transposition occurs during the oxidation. 

The allylic hydroperoxides generated by singlet oxygen oxidation are normally reduced to the corresponding allylic alcohol. The net synthetic transformation is then formation of an allylic alcohol with transposition of the double bond. 

The equivalent to allylic oxidation of alkenes, but with allylic transposition of the carbon-carbon double bond, can be carried out by an indirect oxidative process involving addition of an electrophilic arylselenenyl reagent, followed by oxidative elimination of selenium. In one procedure, addition of an arylselenenyl halide is followed by solvolysis and oxidative elimination. 

The 1,2-carbonyl transposition takes place through the enJo-epoxide 18 easily prepared through the tosylhydrazone 16, followed by regioselective cleavage to the less substituted double bond (17) with 2 equivalents of methyllithium [4] and epoxidation with MCPBA in chloroform from the more accesible convex face of the decalin system. 

The introduction of the double bond of rac-14 was performed by conversion of rac-13 into its a-phenylselenide, subsequent peroxide oxidation, and elimination. Following the synthesis reported by Mehta and Srinivas, an alkylative enone transposition was used as the last step towards irradiation... 

Subsequent hydride shift-mediated oxygen transposition should then generate 370. The furanophane 367 in turn, featuring a trisubstituted double bond with ( )-configuration (necessary for the success of the TADA reaction), was to be generated by RCM. 

A simple transposition of a C=C bond occurs during metabolism of the common fatty acid oleic acid (see Fig. 17-9), and you will encounter some spectacular examples of double-bond repositioning in the synthesis of cholesterol (see Fig. 21-35). 

There are two general pathways for transposition in bacteria. In direct or simple transposition (Fig. 25-43, left), cuts on each side of the transposon excise it, and the transposon moves to a new location. This leaves a double-strand break in the donor DNA that must be... 

DNA transposition 978 meiosis 979 branch migration 980 double-strand break repair model 980 Holliday intermediate 980... 

Benzylidenechroman-4-ones are readily prepared by the condensation of chroman-4-ones with aromatic aldehydes. The exocyclic-endocyclic migration of the double bond has been achieved on heating the chromanone in xylene in the presence of Raney nickel (74JIC281). Rhodium chloride in ethanol is more effective, leading to almost quantitative bond transposition (77JCS(P1)359). 

See page 229, Section 4 for reduction with double bond transposition. 

See also page 47, Section 93 and page 49, Section 9.4, for reduction of sulfur-containing derivatives of alcohols and phenols and page 229, Section 4, for reduction of allylic sulfonates and sulfones with double bond transposition. 

See page 991, Section 1, for addition to the double bond and page 231, Section 5, for oxidation with allylic transposition. 

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