Ozono lysis

Further functionalization has been carried out in the mixed benzo-binaphtho crown shown in Eq. (3.55). Using 2-allylcatechol as starting material, the mixed crown was prepared in the usual fashion. The allyl group was isomerized to a propenyl substituent by treatment with potassium f-butoxide in a benzene/f-butanol mixture. Selective ozono-lysis affords the aldehyde. 

A facile synthesis of cyclic five-, six-, and seven-membered oxonitriles 7-35 by a combination of an ozono lysis and an aldol reaction has been described by the Fleming group [17]. As starting material the unsaturated oxonitriles 7-33 are used, which are easily accessible by reaction of unsaturated esters 7-32 with LiCHjCN (Scheme 7.11). It can be assumed that 7-34 acts as an intermediate. 

There are examples in the literature of the formation of epoxides during ozono-lysis of olefins 269... 

Since allyl sulfoxides may quite easily undergo racemization at the sulfur atom via a reversible [2,3] sigmatropic process, the configurationally more stable chiral allylic phosphine oxides were also investigated.201 Compounds (184) and (185), prepared as a 1 1 mixture from allylphosphonyl dichloride and (-)-ephedrine, were shown to add to cycloalkenones with reasonably high diastereoselectivities. Ozono-lysis of the initially formed 1,4-adducts affords the respective optically active ketoaldehydes (Scheme 67). With a / /-isopropyl-substituted derivative even higher selectivities (88-98% ee) could be obtained. 

The synthesis of unsymmetrical 1,4-diketones results from the conjugate addition of the nitronate anion (as the acyl anion equivalent) to an a,fi-unsaturated ketone [Method (6)].l47a The intermediate nitroketone is converted into the diketone by reduction with titanium(m) chloride at pH 1, or by ozono-lysis of the nitronate anion147b (cf. Section 5.7.7, p. 599). 

The sequence of cyclohexene cleavage and aldol reaction on the dicarbonyl product gives ring-contracted cyclopentenes. This proved particularly valuable when Iwata6 wanted to make subergorgic acid 41 that has three five-membered rings awkwardly joined around a quaternary carbon atom. So crowded are these compounds that they are difficult to draw clearly. Ozono-lysis of the synthetic cyclohexene 38 gave the unstable dialdehyde 39 that cyclised by an aldol condensation to 40 and hence could be oxidised to 41. 

Splitting, or the hydrolysis of triglycerides is usually performed with high-pressure steam, resulting in the formation of split crude fatty acids and glycerin. The production of fatty acids by more sophisticated splitting processes, such as hydrolysis of fatty methyl esters, ozono lysis of unsaturated fatty acids, and chemical oxidation is practiced in special situations. 

When hydroxy and carbaldehyde groups are positioned as vicinal substituents on a cyclic scaffold, enzymatic DHAP addition will effect a ring anulation by a pyranose [ 111 ]. In this respect, the dihydroxydialdehyde 43 generated by ozono-lysis of exo-norbornenediol 42 [99] seemed to be a promising platform for a tandem sequence towards twofold pyranose anulation (Scheme 9). FruA catalysis indeed induced the desired aldolization to furnish a unique bisadduct in 20 %... 

Reduction of naphthalene by Li metal in C2HSNH2 gives a 52% yield of 1,2,3,4,5,6,7,8-octahydronaphthalene. (a) What will this compouhd yield upon ozono-lysis ... 

Firm evidence for the absolute configuration of (— )-deoxynupharidine (26) has been obtained. The enantiomeric structure had been previously proposed on the basis of formation of optically active methylsuccinic acid from the ozono-lysis of a Hofmann degradation product. The ambiguity in this assignment was noted and the absolute configuration was established by correlation with R-( — )-a-methyladipic acid which was prepared in two steps from R-(+)-3-methylcyclo-hexanone. Thus the earlier assignment" is incorrect. Dendrine (27 R = CH2C02Me) has been synthesised by treatment of dendrobine (27, R = H) with iV-bromosuccinimide followed by a Reformatsky-type reaction. ... 

Selenophenylation of the acyclo unsaturated ester 73 followed by desele-nophenyation of 74 gave the 2-(/3-D-ribofuranosyI)acrylic ester 75. Ozono-lysis of 75 and cyclization of 71 with carboxamidomethylene triphenyl-phosphorane gave the 0-protected showdomycin 72 [84JCS(P1)657] (Scheme 12). 

The importance of this steric effect was verified by carrying out the ozono-lysis of acetal 103. Oxidation of 103 by ozone gave the ester 105 exclusively (33). In this reaction, the hydrotrioxide intermediate 104 has proper electron pair orientation to favor the opening in both directions, but cleavage occurs in only one, yielding IPS because of this steric decompression factor. 

Synthetically useful ozonolyses of heteroaromatic systems include the preparation of pyridine derivatives from quinolines (eq 22), the preparation of versatile A-acyl amides by the ozono-lysis of imidazoles (eq 23), and the unmasking of a latent carboxylic acid function by theozonolysisof a furan system (eq 24). ... 

The acid moiety was converted to an amine and the alkene moiety in 5.223 was converted to a nitrile and, thereby, to an acid.55 This sequence for accomplishing this reacted 5.223 with urea to give 5.224. Reduction followed by acylation and ozono-lysis (with a reductive workup) gave 5.225. 5 Conversion to the chloride and displacement with cyanide gave 5.226 and acid hydrolysis led to 5-meihyl-7-amino-heptanoic acid, 5.227. In this lengthy sequence, the acid moiety in 5.223 functioned as the amine precursor and the alkenyl group functioned as the eventual acid moiety. 

Marion (63, 64) clarified the nature of the new lactones and interpreted their mode of formation. They showed that XVI formed an 0,A-diacetyl derivative, added 1 mole of hydrogen, and gave formaldehyde on ozono-lysis, while XVII gave an A-acetyl derivative which furnished formaldehyde on ozonolysis. They rationalized the formation of the three products by assuming that chromous chloride acted in the same way as Zn in a neutral or acidic medium. Indeed, annotinine chlorohydrin was reported (62) to yield both III and XVI on prolonged treatment under Clemmensen conditions. They proposed that compound III formed by a... 

Ozono lysis n Oxidation of an organic material by means of ozone. 

Meldrum s acid is alkylated under phase-transfer conditions, which do not cause ring-opening. Oxo-Meldrum s acid is prepared, in 61 % yield, by ozono-lysis of (methoxymethylene)-Meldrum s acid. The piperidine diester (82)... 

Modifications of unsaturated f. include - hydrogenation and isomerization (cis-tmns) (- isomerism) of the double bonds. Addition reactions, - ozono-lysis and - metathesis are other possibilities for modifying unsaturated f More than one double bond enables conjugation (-+isomerism) and - dimerization. 

O. has a long history, is based on RR, uses many modem technologies today (->splitting, - hydrogenation, ->sulfonation, - epoxidation, - ozono-lysis, - alkoxylation and many others), and comprises a huge number of product groups (- fatty... 

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