Subject reductive carbonylation

When subjected to catalytic hydrogenation with 10% Pd/C in ethyl acetate, porphycene 3.2 was found to be reduced to the 2,3-dihydroporphycene 3.90. Interestingly, this same 2,3-dihydroporphycene 3.90 was also obtained as a side-product (ca. 1 % yield) when the reductive carbonyl coupling of diformyl bipyrrole... 

The transfer of an inorganic ion such as OH from one phase to another is called phase transfer, and the tetraalkylammonium salt is referred t as a phase-transfer catalyst. Many different kinds of organic reactions, includ ing oxidations, reductions, carbonyl-group alkylations, and 8 2 reaction an subject to phase-transfer catalysis, often with considerable improvements ii yield. 8 2 reactions are particularly good candidates for phase-transfi-catalysis because inorganic nucleophiles can be transferred from an aqut ous (protic) phase to an organic (aprotic) phase, where they are much mort reactive. For example ... 

Reductive carbonylation of nitro compounds, especially nitroaromatic compounds according to eq. (1), has been the subject of thorough industrial research starting in 1962 and continuing until the beginning of the 1990s due to the demand for a new, phosgene-free method for the production of isocyanates [1] and the discussions on the chlorine cycle in industry. 

C) but did not return to the initial value (Section A) within 40 min. The addition of 15% water vapor (Section D) further decreased the sulfur dioxide removal efficiency. Curve b in Figure 2 depicts the analyses of carbon dioxide when the bauxite catalyst was subjected to the water treatment. The mirror image resemblance of curves b and a in Figure 2 suggests that the reaction stoichiometry is closely represented by Equation 1 and that the poisoning effect of water is essentially caused by its competition for chemisorption on the alumina Lewis acid sites with the sulfur precursor of the intermediate (9) reductant carbonyl sulfide. 

Metal-catalyzed reductive carbonylation of nitroaromatics using CO has been the subject of intensive investigation in recent years because of the commercial importance of amines, urethanes, and isocyanates (1). Biphasic operation could offer interesting horizons regarding the ease of catalyst recycling. Thus, palladium catalysts have been applied in the presence of water-soluble ligands such as TPPTS or BINAS (2) for the carbonylation of substituted nitroaromatics (Scheme 1). 

Pure piperitone was subjected to the action of purified hydrogen, in the presence of a nickel catalyst, for six hours, the temperature ranging between 175° to 180° C. The double bond in piperitone was readily opened out with the formation of menthone, but further action of the hydrogen under these conditions did not reduce the carbonyl group, even after continued treatment for two days. Under correct conditions, however, the reduction to menthol should take place. The ease with which menthone is formed in this way is of special interest, not only in connection with the production of this ketone, but also as a stage in the manufacture of menthol. 

The homology between 22 and 21 is obviously very close. After lithium aluminum hydride reduction of the ethoxycarbonyl function in 22, oxidation of the resultant primary alcohol with PCC furnishes aldehyde 34. Subjection of 34 to sequential carbonyl addition, oxidation, and deprotection reactions then provides ketone 21 (31% overall yield from (—)-33). By virtue of its symmetry, the dextrorotatory monobenzyl ether, (/ )-(+)-33, can also be converted to compound 21, with the same absolute configuration as that derived from (S)-(-)-33, by using a synthetic route that differs only slightly from the one already described. 

Et2Zn also participates in the reductive coupling as a formal hydride source. Results for the Ni-catalyzed, Et2Zn-promoted homoallylation of carbonyl compounds with isoprene are summarized in Table 7 [30]. Et2Zn is so reactive that for the reaction with reactive aromatic aldehydes it causes direct ethylation of aldehydes, and the yields of homoallylation are diminished (runs 1 and 2). Unsaturated aldehydes seem to be subject to the Michael addition of Et2Zn. Accordingly, for the reaction with cinnamaldehyde, none of the expected homoallylation product is produced instead, the 1,4-addition product of Et2Zn, 3-phenylpentanal is produced exclusively (run 3). 

That molecule is then subjected to the standard carbonyl reduction, Birch reaction, oxidation, ethynylation and, finally, hydrolysis sequence (see 50 to 53). Hydrolysis of the enol ether under more strenuous conditions than was employed with 53 gives the conjugated ketone 65. The carbonyl group is then reduced to afford the corresponding 3p-alcohol (66). Exhaustive acetylation affords the potent oral progestin methynodiol diacetate (67). 

To illustrate the overall magnitude of the mechanistic problem, let us consider the varied reactivity of a prototypical carbonyl compound such as acetone, which is subject to many diverse reactions such as addition, substitution, cycloaddition, oxidation, reduction, etc., as illustrated in Chart 2. 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

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