Through Rearrangements

For a detailed discussion of the acid-catalyzed rearrangement of morphin-andienones and the base-catalyzed rearrangement of neoproaporphine-borane complexes to the dibenzazonine skeleton, see Sec. 10.2.3. 

Of Neospirenes. The nonphenolic benzylisoquinoline iV-formyl-norlaudanosine was oxidized with vanadium oxytrifluoride in trifluoroacetic acid to the neospirene 9 whose structure was established by X-ray analysis. Lithium aluminum hydride reduction of the corresponding ketal 10 supplied 0-methylerybidine  

Of Neoproaporphines. Oxidation of norprotosinomenine trifluor-acetamide with vanadium oxytrifluoride gave the phenolic neoproaporphine 11. Alkaline hydrolysis and bond cleavage, followed by borohydride reduction of the imine bond, supplied the dibenzazonine base 12 in good yield.  

Of Morphinandienols. The natural base laurifonine has been synthesized by a route that may parallel the biogenetic pathway for the formation of this and related alkaloids. O-Methylflavinantine was reduced with sodium borohydride to supply a separable mixture of epimeric dienols. Skeletal rearrangement of the mixture to the neospirene 13 was effected by boron trifluoride-etherate, and subsequent catalytic reduction produced laurifonine in excellent yield  

A related dienol-benzene rearrangement is that of the dihydroneopro-aporphine 14. Reaction with boron trifluoride-etherate or concentrated hydrochloric acid at room temperature gave exclusively the deoxyaporphine 15. No laurifonine was obtained from this reaction.  

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Extensions of 1,3-dipolar additions of aromatic azides (720,721) to other enamines (636), and particularly to the enamine tautomer of SchilTs bases, were explored (722,723). Further nitrone additions were reported (724,725) and a double nitrile oxide added to an endiamine (647). Cyanogen azide and enamines gave cyanoamidines through rearrangement (726). 

The preparation of isothiazolidin-3-one 5-oxide and 5,5-dioxide derivatives of azetidin-3-ones was described (99EUP100069), starting from penicillanic acid sulfoxide amides in the presence of halogenating agents in anhydrous inert solvents or even without them. Through rearrangement and oxidation with conventional methods, compounds 73 could be obtained. For some derivatives the usefulness, as intermediates for the preparation of novel p-lactam analogs or active substances in formulations for antimicrobial therapy, is claimed. 

Pyrroline formation through rearrangement of vinylaziridines was first reported with 1-vinylaziridine derivatives by Whitlock and Smith (Scheme 2.47) [73]. So-... 

Thus appetite has (rightly) grown to obtain [m n] coronanes, 87 (and their homologs) through rearrangement of the appropriate rotanes 36). 

Route C in Figure 3 is a novel mechanistic proposal [28] for the central part of the Dotz reaction that invokes formation of a chromahexatriene intermediate 19 through rearrangement of the branch point species 13, followed by insertion of a CO ligand to yield 15 in the subsequent step. 

Decomposition of 18 under thermal conditions in the presence of acetone in hydrocarbon solvent led to the formation of 23 and 24. These were shown to arise through rearrangement of the chloroepoxide (22) formed upon collapse of ylide 19. Thermolysis in the presence of excess acetone and a substituted benzaldehyde led to a 53% yield of 21, formed by an initial dipolar cycloaddition with the substituted benzaldehyde and ylide 19 to generate dioxolane 20. Dehydrochlorination of 20 yielded 21. 

A subsequent theory [6] allowed for movement of the crosslink junctions through rearrangement of the chains and also accounted for the presence of terminal chains in the network structure. Terminal chains are those that are bound at one end by a crosslink but the other end is free. These terminal chains will not contribute to the elastic recovery of the network. This phantom network theory describes the shear modulus as... 

Dimethylpropane91 (neopentane) is transformed to a mixture of ethyldi-methylcarboxonium ion (21) and dimethylmethylcarboxonium ion (15). At —78°C 21 is formed exclusively. At temperatures higher than -20°C, 15 becomes the predominant product. Formation of 21 can be best explained by a reaction path that involves insertion of protonated ozone into the C—H a bond, formation of the tert-amyl cation through rearrangement, and its quenching by ozone ... 

In contrast with the cyanopyrroles, photolysis of 2-nitropyrrole yields 3-oximino-A4-pyrrolin-2-one through rearrangement to the pyrrolyl nitrite and N—O cleavage to produce a radical pair, which recombine to yield the product (B-77MI30500). 

Through rearranging equations 5.27 and 5.28 to the form of equation 5.8 and inspecting the denominator, we can obtain an observed pKa given by... 

Density is defined as the concentration of matter, measured by the mass per unit volume [1]. The molar volume, Vm, is defined as the volume occupied by 1 mol of a substance. The molar volume of an ideal gas is 22.4140dm3mol-1 (22.4140liter mol-1) at 1 atm pressure and 0°C. Vapor densities pv are derived through rearrangement of the ideal gas law equation as... 

An important method of preparing carbonyl (and hydroxy) compounds, especially on an industrial scale, is through rearrangements of alkyl hydroperoxides ... 

Potts, Ehrlinger, and Nichols573 treated the mesoionic 1,3-thiazine betaine (92) with DMAD and obtained the thiophene 94 (28% yield), which was also synthesized from 97 and DMAD. Some 96 (R = 4-MeOC6H4) was also formed through rearrangement of the starting material. Product 94 could arise from 93 by loss of phenyl isocyanate or from 95 by loss of carbon monoxide. Replacement of the p-methoxy-... 

Dienones, which because of the electron deficiency induced at the carbonyl carbon may be regarded as analogs of pentadienyl cations, are known to close photochemically.103 These closures occur readily in cyclic systems where the geometry requires the disrotatory mode, but the proposed intermediate product, formally a 1,3 diradical, is ordinarily stabilized through rearrangement.104 Woodward and co-workers have demonstrated the predicted photochemical... 

In an interesting and unusual reaction, Paquette and Maynard have shown that peracid oxidation of l,2-disiIyl-3,3-dimethylcyclopropene gives rise to an o -silyl-aq/i-unsaturated acyl silane, through rearrangement of the intermediate epoxycyclopropane. Further treatment with peracid gave the a-epoxy acyl silane (Scheme 54)145. 

B. S. Synthesis of isochroman-3-ylacetates and isochromane-y-lactones through rearrangement of aryldioxolanylacetates./. Chem. Soe. Perkin Trans. 1 1998, 3949-3956. 

A synthetic method for the prepararation of cyclobutanones via an intramolecular cyclization of a ketone enolate has been reported.83 Enol triflates having a silyloxy group at the ft-position under the influence of TBAF give a cyclobutanone or a four-membered enol ether through rearrangement of the trifluoromethanesulfonyl group followed by an intramolecular C- or O-alkylation reaction (Scheme 49). 

When sodium acetate is added to aryldiazonium salts, aryldiazo acetates, R—N=N—OCOCH3, are probably formed through rearrangement of the aryldiazonium salts initially produced, and they react in the same manner as the aryldiazo hydroxides. The aryldiazo acetates are probably the reactive intermediates also in the procedure in which a stabilized diazonium salt is treated with sodium acetate and acetic anhydride in the presence of an aromatic compound. 

Rearrangements of propargyl esters with silver salts were first mentioned by Zakharova in the mid-1940s.49 He described the conversion of 3-chloro-3-methyl-but-l-yne into a mixture of acetates in which the allenic acetate, l-acetoxy-3-methylbut-1,2-diene, was the major compound (Scheme 3.30). Although this product could arise from a silver assisted SN2 reaction, it could also be produced from the substitution product through rearrangement, probably catalyzed by silver ions. 

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