Trans-decalone

Naphthol 1 cA-decalin (12), 1-hydroxy decalin (37), trans- 1-decalone (51)... 

The ring carbons of the /rans -4-oxodccal i n, (e) of Table 4, lie in the same back octants as those of trans-1 -decalone (a) These perturbers should thus sum to a negative CD. The... 

Product ratios of tertiary alcohols obtained from reduction of trans-2-decalone with MCjAl in benzene were similar to those obtained with 4-t-butylcyclohexanone. With a ratio of MejAl to ketone of unity trans-1-decalone gave ca. 93% axial alcohol, and at ratios greater than unity the proportion of axial alcohol dropped to ca. 40%, presumably on account of steric hindrance. The product ratios obtained from cis-and trans-l- and -2-decalones were also discussed. 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

In fact, a similar intramolecular cyclisation was studied by Reusch [11] and he found a remarkable methyl substituent effect on the aldol equilibrium. Starting from the cis-decalones 25 (easily prepared from the Wieland-Miescher ketone), in which the angular methyl group prevents isomerisation to the more stable trans-decalone, it was found that other methyl groups may exert profound but less... 

The stereoselectivity is enhanced if there is an alkyl substituent at C-l. The factors operating in this case are similar to those described for 4-t-butyIcycI ohcxanonc. The trans-decalone framework is conformationally rigid. Axial attack from the lower face leads directly to the chair conformation of the product. The 1-alkyl group enhances this... 

Wu, Y.-D. Tucker, J. A. Houk, K. N. Stereoselectivities of nucleophilic additions to cyclohexanones substituted by polar groups. Experimental investigation of reductions of trans-decalones and theoretical studies of cyclohexanone reductions. The influence of remote electrostatic effects, J. Am. Chem. Soc. 1991,113, 5018-5027. 

Scheme 1 Oxodicarboxylate (4) was converted to trans-decalone (6) whose enolacetate (7) on epoxydation followed by acid treatment yields oxoacetate (9), which was transformated to another oxoacetate (10). It was subjected to standard organic reactions to obtain compound (15). Decarboxylation followed by treatment with base and then triphenylmethyl fluoroborate afforded glutinosone (1) in 30% yield...

However, the relation between stereoselectivity of hydrogenation and solvents polarity is not always so clear as shown by the hydrogenation of P-octalone 9 to trans decalone-3 iO and cis-decalone-3 U. (6). 

Asymmetric cyclic hydroboration. As illustrated in the following equation, the facile accessibility of this reagent by in situ reduction of the dichloroborane derivative with MejSiH and the high optical yield of (+)-trans-decalone prepared from the hydroboration route suggest a general approach to such ketones ... 

An elegant synthesis of Warburganal (12) from the ketone (2) was reported by Kende and Blacklock [8] as depicted in Tig (1)". The ketone (2), prepared [3] by Robinson annelation of the 2-methyl-1,3-cyclohexanedione with ethyl vinyl ketone, on ketalization afforded (3) which was converted to the trans-decalone (4) by the reductive methylation procedure of Stork [9]. Wolff-Kishner reduction of (4) produced the ketal (5), which without purification was hydrolyzed with acid to obtain the trans-decalone (6) [10] in excellent yield. The present method for the synthesis of the decalone (6) appears more efficient and convenient than the methods previously reported [11,12], considering the overall yield and the stereoselectivity. 

Earlier work by Heathcock and co-workers " and Halsall and Thomas suggested that catalytic hydrogenation should yield a cis-fused product (165 - 166, Scheme 22). On the other hand, the ester 178 hydrogenates to a mixture of trans-decalone (179), lactone (180), and a hydrogenolysis product. 

Kirk and Klyne have made a detailed empirical analysis of the circular dichroism of cis- and trans-decalones and related systems. 

Optical resolution of trans-1 -decalol, trans-2 -decalol has been carried out and conversions into trans-decalones of high optical purity have been effected. trans-syn-trans-Perhydroanthracen-2. -ol was also resolved and converted into the ketone. 

Figure 1. Rotatory dispersion of l/ 9/ -dimethyl-trans-decalone-3. (Data supplied by C. Djerassi of Stanford University- See L. H. Zalkow, F. X. Markley, and C. Djerassi, J. Am. Chem. Soc., 82, 6354 (I960).)...

Keto-enol tautomerization can sometimes be used to convert a less stable epimer to a more stable one. This equilibration process is an example of epimerization. An example is the epimerization of cw-decalone to tran -decalone ... 

Write a mechanism using sodium ethoxide in ethanol for the epimerization of cw-decalone to tra 5-decalone. Draw chair conformational stractures that show why tra 5-decalone is more stable than ds-decalone. You may find it helpful to also examine handheld molecular models of cis- and trans-decalone. 

The stereoselectivity is enhanced if there is an alkyl substituent at C-1. The factors operating in this case are similar to those described for 4-t-butylcyclohexanone. The trans-decalone framework is conformationally rigid. Axial attack from the lower face leads directly to the chair conformation of the product. The 1-alkyl group enhances this stereoselectivity because a steric interaction with the solvated enolate oxygen distorts the enolate in such a way as to favor the axial attack. The placement of an axial methyl group at C-10 in a 2(l)-decalone enolate introduces a 1,3-diaxial interaction with the approaching electrophile. As a result, the preferred alkylation product is that resulting from approach on the other side of the enolate. 

The direction of enolization is determined by the comparative stability of the enols formed. Consequently, in accordance with the above discussion (p. 49), in the cis-/3-decalone (171) system enolization will take place predominantly with the splitting out of a proton from C4 (172) and in the trans-/ -decalone (173) system from C2 (174). 

In the case of trans-decalones of type (178), the axial attack of an electrophilic reagent takes place predominantly from the j8-side, in consequence of which compounds containing a methyl group at C q form products with the unnatural lOce-configuration. In this case, obviously, the order of introduction of the substituents will not be immaterial. Consequently, the methylation of 19-nor compounds already containing an oxobutyl chain at Cjo will lead predominantly to the 10/3-methyl derivative (Schemes 73, 111). 

To add rings B and A to the diketone (100), Stork [13] first used the comparatively readily accessible [1053] 4-chloromethyl-3-methylisoxazoles as alkylating agents. The alkylation of the sodium enolate of the bicyclic diketones (100) with 3,5-dimethyl-4-chloromethylisoxazole led to compound (376) in good yield. The reduction of the A -bond in it did not affect the isoxazole ring, forming the trans-decalone (377). The transformation of the isoxazolylmethyl residue into the desired tricyclic system (383) was readily effected by the action of boron trifluoride etherate with subsequent treatment with bases in this case an intermediate was the diketone (380). 

Zhang and Danishefsky reported the first total synthesis of ( )-2 [13]. Their retrosynthetic plan for ( )-2 is illustrated in Scheme 1. The first cmcial step in this contemplated scheme is envisaged to start with the stereoselective Eschenmoser-Claisen rearrangement [15] of allyl alcohol 13 to constmct the requisite transdecalm portion 11 via intermediate 12. Rearrangement precursor 13 is accessible starting fi-om ( )-5-methyl-Wieland-Miescher ketone (15) via trans-decalone 14. The second critical step is envisioned to involve the aldol-type coupling reaction of methyl ester 10 with the known aldehyde 9 [16] to assemble the requisite... 

In the following example, a mixture of the cis- and tran s-decalones is converted completely to the cw-isomer—in general, the thermodynamically less favored isomer ... 

In this experiment, advantage is made of the fact that lithium-ammonia reduction usually proceeds to give trans-fused Decalins 4). Thus, hydrogenation of A -octal one-2 over palladium catalyst gives essentially cw-2-decalone as the product, whereas the lithium-ammonia reduction of the octalone gives the trans ring fusion. 

The bromination given in the preceding experiment may be applied to trans-lO-methyl-2-decalone prepared in Chapter 3, Section III. The product is recrystallized from petroleum ether-benzene (10 1) giving colorless needles, mp 101-103°. 

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