Camphor formation

Interesting pattern formations also occur in surfactants spreading on water due to a hydrodynamic instability [52]. The spreading velocity from a crystal may vary with direction, depending on the contour and crystal facet. There may be sufficient imbalance to cause the solid particle to move around rapidly, as does camphor when placed on a clean water surface. The many such effects have been reviewed by Stemling and Scriven [53]. 

The theory of sublimation, t.e. the direct conversion from the vapour to the sohd state without the intermediate formation of the liquid state, has been discussed in Section 1,19. The number of compounds which can be purified by sublimation under normal pressure is comparatively small (these include naphthalene, anthracene, benzoic acid, hexachloroethane, camphor, and the quinones). The process does, in general, yield products of high purity, but considerable loss of product may occur. 

Starting material camphor quinone (Chapter 1, Section XI) and resulting in the formation of Horner s acid (5). 

The C2-symmetric epoxide 23 (Scheme 7) reacts smoothly with carbon nucleophiles. For example, treatment of 23 with lithium dimethylcuprate proceeds with inversion of configuration, resulting in the formation of alcohol 28. An important consequence of the C2 symmetry of 23 is that the attack of the organometallic reagent upon either one of the two epoxide carbons produces the same product. After simultaneous hydrogenolysis of the two benzyl ethers in 28, protection of the 1,2-diol as an acetonide ring can be easily achieved by the use of 2,2-dimethoxypropane and camphor-sulfonic acid (CSA). It is necessary to briefly expose the crude product from the latter reaction to methanol and CSA so that the mixed acyclic ketal can be cleaved (see 29—>30). Oxidation of alcohol 30 with pyridinium chlorochromate (PCC) provides alde-... 

This contrary stereochemistry in the Bucherer - Bergs reaction of camphor has been attributed to steric hindrance of e.w-attack of the cyanide ion on the intermediate imine. Normally, equatorial approach of the cyanide ion is preferred, giving the axial (t>Mr/o)-amino nitrile by kinetic control. This isomer is trapped under Bucherer-Bergs conditions via urea and hydan-toin formation. In the Strecker reaction, thermodynamic control of the amino nitrile formation leads to an excess of the more stable compound with an equatorial (e.w)-amino and an axial (endo)-cyano (or carboxylic) function13-17. 

Several methods for asymmetric C —C bond formation have been developed based on the 1,4-addition of chiral nonracemic azaenolates derived from optically active imines or enamines. These methods are closely related to the Enders and Schollkopf procedures. A notable advantage of all these methods is the ready removal of the auxiliary group. Two types of auxiliaries were generally used to prepare the Michael donor chiral ketones, such as camphor or 2-hydroxy-3-pinanone chiral amines, in particular 1-phenylethanamine, and amino alcohol and amino acid derivatives. 

Corey and Chaykovsky were the first to investigate the reaction of dimethyl sulphoxide anion (dimsyl anion) with aldehydes and ketones400,401. They found that the reaction with non-enolizable carbonyl compounds results in the formation of /1-hydroxyalkyl sulphoxides in good yields (e.g. Ph2CO—86%, PhCHO—50%). However, with enolizable carbonyl compounds, particularly with cycloalkanones, poor yields of hydroxyalkyl products are observed (e.g. camphor—28%, cyclohexanone—17%, but... 

This reaction is equally amenable to enals with both aliphatic and aromatic P-substituents, althongh the formation of substitnted cyclohexanes (from analogous enals) proceeds with rednced enantioselectivity (Scheme 12.51) [92], You and co-workers have shown that the same reaction is also promoted by triazolinm salts derived from camphor in excellent enantioselectivity (95-99% ee) [93]). 

Studies of the intramolecular cyclization of P-amino acids have included the use of camphor-derived oxazoline A-oxide 66 and a [3+2] cycloaddition reaction as a step in the formation of the amino acid with the required stereochemistry <00OL1053, OOEJOC1595>. A diastereoselective synthesis of a ip-methylcarbapenem intermediate utilises a cyclization of a P-amino acid <99CC2365>. 

The reaction of diethylzinc or dimethylzinc with prochiral ketones, in the presence of a stoichiometric amount of Ti(OPr )4 and a catalytic amount (20%) of camphor-sulfonamide derivative 136, leads to the formation of the corresponding tertiary alcohols with enantiomeric ratios of up to 94.5 5.5. 

Asymmetric cyclopropanol formation has been achieved with olefmic acylsulfonamides, which act like olefmic esters. Thus, their reaction with 1 provides a method for synthesizing cyclopropanols in an optically active form. As represented by Eq. 9.41, alkylation of Oppolzer s camphor sultam and reaction of the resulting unsaturated acylsulfonamides with 1 provides optically active bicyclic cyclopropanols having exclusively the structure shown in the equation [76],... 

Further evidence for the formation of intermediate compounds in catalytic reactions is afforded by the observation (a) that optically active camphor is formed from optically inactive (racemic) camphor carboxylic acid in the presence of the d- or /-forms of quinine, quinidine or nicotine and (6) that optically active bases, e.g., quinidine, catalyze the synthesis of optically active mandelonitrile from benzaldehyde and hydrocyanic acid.10 These results hardly admit of any other interpretation than the intermittent production of a catalyst-reactant compound. 

Horeau and co-workers (130) found that an ether solution containing four molar equivalents of (+ )-camphor added to one molar equivalent of LAH, followed by addition of A1C13, reduced 2-butanone or pinacolone. The reagent involved is presumably the same as that prepared by Eliel and Nasipuri (111), although the reaction leading to the formation of 111 is different (eq. [29]). The... 

Fluorotrichloromethane, see Trichlorofluoromethane Fly-die, see Dichlorvos Fly fighter, see Dichlorvos FMC 5462, see a-Endosulfan, p-Endosulfan FMC 10242, see Carbofuran Foliclol, see Parathion Folidol, see Parathion Folidol E 605, see Parathion Folidol E E 605, see Parathion Folidol oil, see Parathion Forane, see 1,1,2-Trichlorotrifluoroethane Foredex 75, see 2,4-D Forlin, see Lindane Formal, see Malathion, Methylal Formaldehyde bis(p-chloroethylacetal), see Bis(2-chloroethoxy) methane Formaldehyde dimethylacetal, see Methylal Formalin, see Formaldehyde Formalin 40, see Formaldehyde Formalith, see Formaldehyde Formic acid, ethyl ester, see Ethyl formate Formic acid, methyl ester, see Methyl formate Formic aldehyde, see Formaldehyde Formic ether, see Ethyl formate Formira, see Formic acid Formisoton, see Formic acid Formol, see Formaldehyde Formosa camphor, see Camphor Formula 40, see 2,4-D... 

Terpenoid DBPs were investigated by Joll et al. [124] and Qi et al. [125]. The main ozonation product of 2-methylisobomeol was camphor, which was further oxidized to formaldehyde, acetaldehyde, propanal, buntanal, glyoxal, and methyl glyoxal [125]. Chlorination of p-carotene, retinol, p-ionone, and geranyl acetate resulted in the formation of THMs [124]. 

Equilibrium studies have shown that the first formation constant of the chromium(iii)-ethylenediamine system is < 10, over 10 -fold smaller than the value (10 ) previously reported. [Cr(en)3 (tn) ] (x = 0—3 and tn = tri-methylenediamine) complexes have been prepared and resolved using nitro-(-f )D-camphor. These mixed complexes have the same absolute configuration, A, as the pure [Cr(en)3] and [Cr(tn)3] species. Selective intervention of an optically active counterion in the relaxation processes of excited enantiomeric complexes can lead to partial resolution. This has been achieved for [Cr(phen)3] using D-tartrate. ... 

This enzyme [EC 1.14.15.1], also known as camphor 5-exo-methylene hydroxylase, and cytochrome P450-cam, catalyzes the reaction of (+)-camphor with putidare-doxin and dioxygen to generate (-F)-exo-5-hydroxy-camphor, oxidized putidaredoxin, and water. A heme-thiolate acts as a cofactor. The enzyme can also utilize ( )-camphor as a substrate, and l,2A-campholide will result in the formation of 5-exo-hydroxy-l,2-campholide. V. Ullrich W. Duppel (1975) The Enzymes, 3rd ed., 12, 253. 

The synthesis of camphor (80% optical purity) by heating optically pure di-hydrocarvone at 400 °C for 20 h is reminiscent of Money s racemic camphor synthesis (Vol. 1, p. 39) in that both correspond to a biogenetic-type synthesis via enol formation. Further synthetic work on deuteriated camphors (see references therein and Vol. 3, p. 67 Vol. 4, p. 48 Vol. 7, p. 38 for earlier work) includes syntheses of optically pure [8- Hi]-, [8- H2]-, and [8- H3]-(—)-camphor (204) by modification of known reactions (Scheme 5) and the use of an improved Zn-Cu... 

Other papers of interest in this section report transamination of camphor-3-carbothioamides with secondary cyclic amines, reaction of camphorquinone with dimethyl /S-ketoglutarate, the use of fenchone (212 X=0) in alkene formation from Grignard reagents, bromination of 2-e/itfo-6-endo-dibromobornane to yield 2,3,6-endo-tribromoborn-2-ene, and camphor-enol trimethylsilyl ether formation by quenching the reaction mixture of butyl-lithium and camphor tosyl-hydrazone with trimethylsilyl chloride. ... 

The formation of spirocyclopropanes from the reaction of diazodiphenylmethane and ( )-8-phenylmenthyl esters of acrylic acid and methyl fumarate occurred with a modest level of diastereofacial selectivity (136). In contrast, diastereoselectivities of 90 10 were achieved in the cycloadditions of diazo(trimethylsilyl)methane with acrylamides 65 derived from camphor sultam as the chiral auxiliary (137) (Scheme 8.16). Interestingly, the initial cycloadducts 66 afforded the nonconjugated A -pyrazolines 67 on protodesilylation the latter were converted into optically active azaproline derivatives 68. In a related manner, acrylamide 69 was converted into A -pyrazolines 70a,b (138). The major diastereoisomer 70a was used to synthesize indolizidine 71. The key step in this synthesis involves the hydrogenolytic cleavage of the pyrazoline ring. 

One problem in the anti-selective Michael additions of A-metalated azomethine ylides is ready epimerization after the stereoselective carbon-carbon bond formation. The use of the camphor imines of ot-amino esters should work effectively because camphor is a readily available bulky chiral ketone. With the camphor auxiliary, high asymmetric induction as well as complete inhibition of the undesired epimerization is expected. The lithium enolates derived from the camphor imines of ot-amino esters have been used by McIntosh s group for asymmetric alkylations (106-109). Their Michael additions to some a, p-unsaturated carbonyl compounds have now been examined, but no diastereoselectivity has been observed (108). It is also known that the A-pinanylidene-substituted a-amino esters function as excellent Michael donors in asymmetric Michael additions (110). Lithiation of the camphor... 

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