Sabina ketone


Alcohols, esters (but not ethyl benzoate, ethyl malonate or ethyl oxalate), aldehydes, methyl ketones and cyclic ketones containing less than nine carbon atoms as well as ethers containing less than seven carbon atoms are soluble in 85 p>er cent, phosphoric acid.  [c.1053]

Because ground-state oxygen is a triplet, spin conservation during the decomposition of the transition state (37) must lead to an excited triplet-state ketone or (excited) singlet oxygen. The emitting species has been found to be the triplet excited state of the carbonyl product (132), although singlet oxygen has also been detected.  [c.269]

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation.  [c.200]

These steric factors are also indicated by the relative basicity of enamines derived from five-, six-, and seven-membered ketones. The five- and seven-membered enamines are considerably stronger bases, indicating better conjugation between the amine lone pair and the double bond. The reduced basicity of the cyclohexanone enamines is related to the preference for exo and endo double bonds in six-membered rings (see Section 3.10).  [c.432]

Although the simple atomic orbital resonance concept (9) (10) can serve as a useful model for the processes discussed so far, it does not take into account certain aspects which may contribute significantly to the chemical properties of the nonconjugated n,n excited ketone. No differentiation is made between the singlet excited state produced directly by absorption of light and the energetically lower triplet state reached from the excited singlet by spin inversion (intersystem crossing) or formed directly by energy transfer from a sensitizer. Further, formaldehyde is known to adopt pyramidal forms in the excited singlet and triplet n,Ti states after vibrational relaxation (with the CO bond longer and its angle with the plane of the CH2 group wider  [c.295]

On the other hand, the cyclic form of the analogous seven- to thirteen-membered compounds is energetically disadvantageous and easy formation of amino ketones is encountered. In accordance with this, the compound unsubstituted in position 2 (1-methyl-l-aza-2-cyclooctene, -nonene, and -decene) can react as acyclic amino aldehydes (176). In the case of enamines bearing an aromatic ring in position 2, especially with seven- and thirteen-membered rings, a higher stability of the cyclic form can be expected. Therefore there is a good possibility for the isolation of the cyclic form.  [c.271]

Similarly, the method has been applied to the synthesis of five- (244) and seven- (245,246) membered-ring ketone analogs of (0-tetralone.  [c.347]

Sabina ketone, Cj Hj O, is not a natural constituent of essential oils, but is of considerable interest on account of its utility in the synthesis of other ketones.  [c.225]

The DuPont Merck group had previously explored a series of peptide-based diols tha were potent inhibitors but with poor oral bioavailability. They were keen to retain th( diol functionality, and so the next step was an expansion of the ring to a seven-memberec diol. The ketone was then changed to a cyclic urea to strengthen the hydrogen bonds tc the flaps and to aid the synthesis. Further modelling studies based upon the X-ray structurt were performed to predict the optimal stereochemistry and the conformation required foi optimal interaction with the enzyme. The results of these studies showed that the 4R, 5S 6S, 7R configuration was most appropriate. Nitrogen substituents were predicted to bine to the S2 and S2 pockets of the enzyme, and so various analogues were synthesised ir order to enhance the potency whilst maintaining the desired pharmacological properties The compound eventually chosen for further studies, leading to clinical trials, was a p-hydroxymethylbenzyl derivative (Figure 12.35).  [c.709]

The 1,6-difunctional hydroxyketone given below contains an octyl chain at the keto group and two chiral centers at C-2 and C-3 (G. Magnusson, 1977). In the first step of the antithesis of this molecule it is best to disconnect the octyl chain and to transform the chiral residue into a cyclic synthon simultaneously. Since we know that ketones can be produced from add derivatives by alkylation (see p. 45ff,), an obvious precursor would be a seven-membered lactone ring, which is opened in synthesis by octyl anion at low temperature. The lactone in turn can be transformed into cis-2,3-dimethyicyclohexanone, which is available by FGI from (2,3-cis)-2,3-dimethylcyclohexanol. The latter can be separated from the commercial ds-trans mixture, e.g. by distillation or chromatography.  [c.206]

Preparation of spirooxaziridines from cyclic ketones poses no problems nor does oxaziridine synthesis from cyclic Schiff bases, which was preferably carried out with pyrro-lines to give, for example (245) (59JCS2102) and, in connection with tranquilizer synthesis, with heterocyclic seven-membered rings to give, for example, (246) (63JOC2459).  [c.228]

Michler s ketone [4,4 -bis(dimethylamino)benzophenone] [90-94-8] M 268.4, m 179", pK 9.84. Dissolved in dilute HCl, filtered and ppted by adding ammonia (to remove water-insoluble impurities such as benzophenone). Then crystd from EtOH or pet ether. [Suppan J Ghent Soc, Faraday TransI 71 539 1975.] It was also purified by dissolving in benzene, then washed with water until the aqueous phase was colourless. The benzene was evaporated off and the residue recrystd three times from benzene and EtOH [Hoshino and Kogure J Phys Ghent 72 417 1988],  [c.303]

To make a photoresist poly(vinyl cinnamate), or a high vinyl cinnamate copolymer, is dissolved in a solvent such as methylene dichloride and the solution is coated uniformly over the substrate by a process such as spin casting. After evaporation of the solvent a masking material (which in the case of a simple demonstration could be a paper clip) is placed on the resist and the assembly is exposed to ultraviolet light. The exposed surfaces are then insolubilised. After exposure the mask is removed and soluble matter dissolved in a solvent such as cellosolve acetate and this exposes the substrate in the shape of the mask. This may then be etehed or otherwise treated as required. By the use of appropriate sensitisers such as, 1,2-benzanthraquinone or Michler s ketone the cross-linking may be brought about by visible light. The cross-linking is believed to involve the produetion of a four-membered cyclobutane ring (Figure 14.9).  [c.396]

NMR The signal for the carbon of C=0 in aldehydes and ketones appears at very low field, some 190-220 ppm downfield from tetranethylsilane. Figure 17.19 illustrates this for 3-heptanone, in which separate signals appear- for each of the seven carbons. The six 5p -hybridized carbons appear- in the range 8 8-42, and the carbon of the C=0 group is at 8 210. Note, too, that the intensity of the peak for the C=0 carbon is much less than all the others, even though each peak conesponds to a single carbon. This decreased intensity is a characteristic of pulsed Fourier transfor-m (FT) spectra for carbons that don t have attached hydrogens.  [c.738]

The rate is affected, not unexpectedly, by two factors the basicity and steric environment of the secondary amino group and the nature and environment of the carbonyl group. Of the secondary amines used, pyrrolidine gives a higher reaction rate than the more weakly basic morpholine, while cyclic amines generaliy produce enamines faster than open-chain ones. This is of course what would be expected, but the fact that pyrrolidine reacts faster than piperidine may deserve comment. The basicity and steric environment of the two bases are closely similar (Pyrrolidine has Ar= 1.3 x 10 , morpholine has K = 2.44 x 10 , and piperidine has Ar= 1.6 x 10. ) and the differences in rate are probably to be ascribed to the different rates of the dehydration steps The transition state with pyrrolidine involves making a trigonal carbon in a five-membered ring and the faster rate of solvolysis of methylcyclopentyl chloride than that of the corresponding cyclohexyl compound (H. C. Brown,7. Chem. Soc., 1956,1248) correlates with the faster formation of an enamine from pyrrolidine than from piperidine. The effect of the ring size in the case of cyclic ketones is also notable cyclopentanone reacts most rapidly, followed by cyclohexanone which is faster than the seven- and higher-membered ketones. If the rate of formation of enamines were solely a reflection of the rate of formation of the intermediate carbinolamines, cyclohexanone would form its enamine faster than cyclopentanone. If, on the other hand, the rate of dehydration of the carbinolamine were the controlling factor, then the seven-membered ring would be faster than the six. Since neither of these orders corresponds to the experimental one, the over-all rate is evidently not solely ascrib-able to any single one of the reversible steps A, B and C involved in the formation of the enamine.  [c.63]

The reaction was also carried out with variously substituted (53-55) and nonmethylated (5d) lactams. Treatment of l-methyl-2-piperidone with phenylmagnesium bromide and subsequent reaction with acetic anhydride gave the corresponding acetate in small yield (57). This indicates that the A arbinolamine salt is an intermediate in this reaction which, on liberation, affords another tautomeric form. In the five- and six-membered series this tautomeric form is a cyclic enamine. Lactams with larger rings, i.e., seven-(58,59), eight- (60), nine- (61), eleven-, and thirteen-membered (62) lactams, yield only acyelic amino ketones (17, = 5-11) when treated with Grignard  [c.257]

Cyclic enamines with an isomeric position of the double bond have been obtained by the addition of Grignard reagents to five- (78-81), six- (82-86), seven- (87-90), and thirteen- (89-91) membered lactams, whereas other medium-sized (92,93) lactams furnished amino ketones. The reaction has been extended to substituted lactams (94-98), and iminoethers (99,100).  [c.323]

The reactions of enamines with aldehydes (329,350) are noteworthy in that they provide a route to the monobenzylidene derivatives of five- to seven-membered eyclic ketones as well as a method for the formation of other a, 9-unsaturated carbonyl compounds, in fair to good yields. The condensation of benzaldehyde with enamines is also involved in the formation of 3,5-dibenzylpyridine from piperidine and benzaldehyde (191-193).  [c.377]

The formation of a-acetoxyketones by oxidation of enamines with thallic acetate has been studied in detail (27) and found to be of preparative value (80 % yields) particularly in five- and six-membered-ring ketone derivatives. Enamines of linear or seven-membered-ring ketones were oxidized also, but at very much slower rates. Enamines of aldehydes with a-hydrogen substituents underwent self-eondensations during the oxidation reactions. Lead tetraacetate was less satisfactory as an oxidizing agent.  [c.412]

Monosaccharides consist typically of three to seven carbon atoms and are described either as aldoses or ketoses, depending on whether the molecule contains an aldehyde function or a ketone group. The simplest aldose is glyceraldehyde, and the simplest ketose is dihydroxyacetone (Figure 7.1). These two simple sugars are termed trioses because they each contain three carbon atoms. The structures and names of a family of aldoses and ketoses with three, four, five, and six carbons are shown in Figure 7.2 and 7.3. Hexoses zlyc the most abundant sugars in nature. Nevertheless, sugars from all these classes are important in metabolism.  [c.210]

As Figures 7.7 and 7.8 imply, in most monosaccharides there are two or more hydroxyl groups which can react with an aldehyde or ketone at the other end of the molecule to form a hemiacetal or hemiketal. Consider the possibilities for glucose, as shown in Figure 7.7. If the C-4 hydroxyl group reacts with the aldehyde of glucose, a five-membered ring is formed, whereas if the C-5 hydroxyl reacts, a six-membered ring is formed. The C-6 hydroxyl does not react effectively because a seven-membered ring is too strained to form a stable hemiacetal. The same is true for the C-2 and C-3 hydroxyls, and thus five-and six-membered rings are by far the most likely to be formed from six-membered monosaccharides. D-Ribose, with five carbons, readily forms either five-membered rings a- or /3-D-ribofuranose) or six-membered rings a- or /3-D-ribopyranose) (Figure 7.8). In general, aldoses and ketoses with five or more carbons can form either furanose or pyranose rings, and the more stable form depends on structural factors. The nature of the substituent groups on the carbonyl and hydroxyl groups and the configuration about the asymmetric carbon will determine whether a given monosaccharide prefers the pyranose or furanose structure. In general, the pyranose form is favored over the furanose ring for aldohexose sugars, although, as we shall see, furanose structures are more stable for ketohexoses.  [c.216]

The most direct evidence for the formation of a complex L—>-l2 in solution comes from the appearance if an intense new charge-transfer band in the near ultraviolet spectrum. Such a band occurs in the region 230-330 nm with a molar extinction coefficient e of the order of 5 X 10 — 5 X lO Imol cm and a half-width typically of 4000-8000 cm . Detailed physicochemical smdies further establish that the formation constants of such complexes span the range 10 — 10 lmol with enthalpies of formation 5-50kJmol . Some typical examples are in Table 17.9. The donor strength of the various solvents (ligands) is rather independent of the particular halogen (or interhalogen) solute and follows the approximate sequence benzene < alkenes < polyalkylbenzenes alkyl iodides alcohols ethers ketones < organic sulfides < organic selenides < amines. Conversely, for a given solvent the relative acceptor strength of the halogens increases in the sequence CI2 < Br2 < I2 < IBr < ICl, i.e. they are class b or soft acceptors (p. 909). Further interactions may also occur in polar solvents leading to ionic dissociation which  [c.807]

Geometrically restricting the diene to a cisoid conformation greatly enhances the formation of the seven-memhered ring. The cycloheptene (97) could be obtained in 65% yield (along with 8% of the spiro-methylenecyclopentane) from the diene (98). Further selective elaboration of (97) demonstrates the versatility of this approach, as the ketone (99) and the dienone (100) can be envisioned as intermediates toward the synthesis of procurcumenol and helispendiolide, respectively. The less sterically hindered diene ester (101) gave exclusively the seven-memhered ring adduct as a mixture of diastereoisomers (Scheme 2.27) [38].  [c.76]

The synthedc ndlity of the Henry reaction is shovm in Scheme 3.1, where fi-nitro alcohols are converted into fi-amino alcohols, amino sugars, ketones and other important compounds.  [c.30]

The nitro group of ct-nitro ketones is readily removed either by treatment v/ith BiuSnH or reduction v/ith LiAlHl of the cotrespondmg tosylhydrazones fEq 3 58 Details of denitration are discussed in Section 7 2, and some applications of this process are shovm in Schemes 35-37  [c.47]

Construction of the carbon frameworks by using the activating property of the nitro group followed by denitration provides a useful tool for the preparation of various naniral products as shovm in Schemes 3 5-3 7 For example, fZ -jasmone and dihydrojasmone, constinients of the essential oilof jasmone flowers, have been prepared as shown in Scheme 3 5 Schemes 3 6 and 3 7 present a synthesis of pheromones via denitration of ct-nitro ketones "  [c.47]

In 1970, a new reacdon, the displacement of a nitro group from ct-nitro esters, ct-nitro nitnles, ct-nitro ketones, iind ct,ct-dinitro compounds by nitroalkiine salts, was described. These displacements, which are exemplified by the reacdon presented in Eq. 7.1, take place at room temperanire iind give excellent yields of pure products. The reacdon proceeds via a radiciil chain mechanism involving one electron-transfer processes as shovmin Scheme 7.1 the details of the mechanism are described in a review.  [c.182]

Although this method is aot a geaeral procedure, bemg specific for ct-nitroketoues, k has several merits to avoid the use of toxic reageuts such as organodn compounds Functionalized ketones have been prepared by this denitration reaction, in which functionalized nitroalkanes are used as alkyl anion synthons For example, 3-nitropropanal ethylene acetal can be used as synthon of the 3-oxo-propyl anion and 1,4-dicarbonyl compounds are prepared, as shovm In Eq 7 88  [c.212]


See pages that mention the term Sabina ketone : [c.71]    [c.225]    [c.226]    [c.226]    [c.877]    [c.151]    [c.159]    [c.779]    [c.224]    [c.472]    [c.416]    [c.600]    [c.258]    [c.826]    [c.100]    [c.78]    [c.192]   
The chemistry of essential oils and artificial perfumes Volume 2 (1922) -- [ c.57 , c.225 ]