Aldehydes 7?,73-1,2- cyclohexane

The decarbonylations, which do not appear to be affected by light, are reasonably selective with aromatic aldehydes, yielding the expected product however, significant amounts of other products are obtained with non-aromatic substrates (e.g. cyclohexane-aldehyde gives methylcyclopentane and small amounts of n-hexane, as well as the expected cyclohexane and cyclohexen-4-al gives both cyclohexene and cyclohexane). Indeed, the unexpected products perhaps provided a major clue to an understanding of the reaction mechanism(s) involved. 

The secondary alcohol can be made by some sort of Grignard chemistry. Cyclohexyl Grignard could be added twice to ethyl formate or once to the cyclohexane aldehyde. 

Concern for the conservation of energy and materials maintains high interest in catalytic and electrochemistry. Oxygen in the presence of metal catalysts is used in CUPROUS ION-CATALYZED OXIDATIVE CLEAVAGE OF AROMATIC o-DIAMINES BY OXYGEN (E,Z)-2,4-HEXADIENEDINITRILE and OXIDATION WITH BIS(SALI-CYLIDENE)ETHYLENEDIIMINOCOBALT(II) (SALCOMINE) 2,6-DI-important industrial method, is accomplished in a convenient lab-scale process in ALDEHYDES FROM OLEFINS CYCLOHEXANE-CARBOXALDEHYDE. An effective and useful electrochemical synthesis is illustrated in the procedure 3,3,6,6-TETRAMETHOXY-1,4-CYCLOHEX ADIENE. ... 

The effect of introducing -hybridized atoms into open-chain molecules was discussed earlier, and it was noted that torsional barriers in 1-alkenes and aldehydes are somewhat smaller than in alkanes. Similar effects are noted when sp centers are incorporated into six-membered rings. Whereas the fiee-energy barrier for ring inversion in cyclohexane is 10.3 kcal/mol, it is reduced to 7.7 kcal/mol in methylenecyclohexane and to 4.9 kcal/mol in cyclohexanone. ... 

According to this concept, the aldol condensation normally occurs through a chairlike transition state. It is further assumed that the stmcture of this transition state is sufficiently similar to that of chair cyclohexane to allow the conformational concepts developed for cyclohexane derivatives to be applied. Thus, in the example above, the reacting aldehyde is shown with R rather than H in the equatorial-like position. The differences in stability of the various transition states, and therefore the product ratios, are governed by the steric interactions between substituents. 

The chiral bicyclic imidazolidine 74 is deprotonated at the 2 position by s-BuLi and the resulting anion adds to alkyl halides, acid chlorides, chlorofor-mates, phenyl isocyanate, and aldehydes. The use of this compound as a chiral formyl anion equivalent seems to be limited, however, since the diastereoselectiv-ity in the addition to aldehydes is poor and hydrolysis of the products 75 to give aldehydes also produces cyclohexane-1,2-diamine, necessitating isolation of the aldehyde as its 2,4-dinitrophenylhydrazone (96SL1109 98T14255). 

S,5S)-5-(2-Alkeny/ideneamiuo)- or (4S,5S)-5-(2-Alkynylideneamino)-2,2-dimt lli)l-4-phenyl-l,3-clioxane 8 Equimolar amounts of an a,/f-unsaluraled aldehyde and (45,55 )-5-amino-2.2-dimethyl-4-phenyl-1,3-diox-ane 7 are mixed with cyclohexane and refluxed for 2 h using a Dean-Stark trap. Then the cyclohexane is removed, the residue is dissolved in Ei,0 and dried over MgSO . Evaporation of the solvent provides imine 8 yield. 90-98%. 

Besitzen Aldehyd und Keton a-H-Atome, so werden diese zunachst durch Hydroxy-methyl-Gruppen ersetzt. Auf diese Weise erhalt man z. B. aus Acetaldehyd und vier Molen Formaldehyd Pentaerythrit (73% d.Th.)4 bzw. aus Cyclohexanon mit fiinf Molen Formaldehyd 2-Hydroxy-1,1,3,3-tetrakis-[hydroxymethyl]-cyclohexan (73-85% d.Th.). Da es sich hierbei zunachst um eine Aufbaureaktion handelt, wird diese Umsetzung in Bd. VI/la/2, S. 1314f. geschlossen abgehandelt (vgl. auch Lit.s). 

In this section primarily reductions of aldehydes, ketones, and esters with sodium, lithium, and potassium in the presence of TCS 14 are discussed closely related reductions with metals such as Zn, Mg, Mn, Sm, Ti, etc., in the presence of TCS 14 are described in Section 13.2. Treatment of ethyl isobutyrate with sodium in the presence of TCS 14 in toluene affords the O-silylated Riihlmann-acyloin-condensation product 1915, which can be readily desilylated to the free acyloin 1916 [119]. Further reactions of methyl or ethyl 1,2- or 1,4-dicarboxylates are discussed elsewhere [120-122]. The same reaction with trimethylsilyl isobutyrate affords the C,0-silylated alcohol 1917, in 72% yield, which is desilylated to 1918 [123] (Scheme 12.34). Likewise, reduction of the diesters 1919 affords the cyclized O-silylated acyloin products 1920 in high yields, which give on saponification the acyloins 1921 [119]. Whereas electroreduction on a Mg-electrode in the presence of MesSiCl 14 converts esters such as ethyl cyclohexane-carboxylate via 1922 and subsequent saponification into acyloins such as 1923 [124], electroreduction of esters such as ethyl cyclohexylcarboxylate using a Mg-electrode without Me3SiCl 14 yields 1,2-ketones such as 1924 [125] (Scheme 12.34). 

Homoenolate Reactivity The ability to generate homoenolates from enals and its application to the preparation of y-butyrolactones 30, through reaction with an aldehyde or aryl trifluoromethyl ketone, was reported independently by Glorius [8], and Bode and Burstein [9] (Scheme 12.4). A sterically demanding NHC catalyst is required to promote reactivity at the d terminus and to prevent competitive benzoin dimerisation. Nair and co-workers have reported a similar spiro-y-lactone formation reaction using cyclic 1,2-diones, including cyclohexane-1,2-dione and substituted isatin derivatives [10]. 

Numerous chiral non-S-coordinating bis(sulfonamides) have been successfully involved in the enantioselective addition of various organozinc reagents to aldehydes since the first use of tr<2 5-l(i ),2(i )-bis(trifluoromethanesulfo-namido)cyclohexane reported in 1989 by Ohno et These authors demonstrated the usefulness of this ligand in the Ti-catalysed enantioselective addition of ZnR2 to a variety of aldehydes, allowing enantioselectivities of up to 99% ee to be obtained (Scheme 3.37). 

Scheme 3.37 7>awi-l(7 ),2(7 )-bis(trifluoromethanesulfonamido)cyclohexane ligand for additions of ZnR2 to aldehydes. 

A recent example where Co2(CO)8 serves as a precatalyst is in the preparation of linear and branched aldehydes via propylene hydroformylation in supercritical C02 (93-186 bar 66-108 °C). Cyclohexane carbaldehyde is produced from cyclohexene using Co2(CO)8 and an acid RCOOH, or else is successful with another established Co catalyst, Co(OOCR)2, assumed to form in situ in the former case. Oligomerization of aldehydes such as n-butanal is achieved with Co2(CO)6L2 as catalyst (L = CO, PR3).1364... 

For example, the parent bicyclo[2.2.1] system 9 affords the epoxy-aldehyde 64 in high yield (97 %) in nonpolar solvents (cyclohexane)62). The mechanism is rationalized in equation 52. Small amounts (ca. 1 %) of the bicyclic ether 65 are also formed, but it is known that 64 rearranges into 65 on heating 62). 

The Prins cyclization can also be coupled with a ring-contraction pinacol rearrangement, as illustrated in Scheme 1.6. This allows a smooth conversion of alkyl-idene-cyclohexane acetal 1-16 to single bond-joined cyclohexane cyclopentane aldehyde 1-17 [le]. 

---