Decalin diols

The allyl boronate 101, prepared by treatment of the cis-decalin diol 100 with trisallylborane, underwent allylation with dihydrocinnamaldehyde to afford the corresponding homoallylic alcohols favoring the R-enantiomer, which was the major enantiomer predicted based on transition-state calculations. Although the level of enantioselectivity realized with 100 is low, further refinements of the computational parameters should lead to the discovery of more efficient chiral ligands.39... 

Since it is necessary to form a cyclic intermediate, not all diols can be used. Consider the set of diasteriomeric diols of Figure 8.5 (enantiomers not shown). It should be clear to you that the dihedral angle subtended between the hydroxyl groups on carbon atoms 2 and 3 in the decalin diols A, C, D, E, and E are all about 60°, while in B, and D, the angle is about 180°. It should also be... 

This dry ozonation procedure is a general method for hydrox-ylation of tertiary carbon atoms in saturated compounds (Table 1). The substitution reaction occurs with predominant retention of configuration. Thus cis-decalin gives the cis-l-decalol, whereas cis- and frans-l,4-dimethylcyclohexane afford cis- and trans-1,4-dimethylcyclohexanol, respectively. The amount of epimeric alcohol formed in these ozonation reactions is usually less than 1%. The tertiary alcohols may be further oxidized to diols by repeating the ozonation however, the yields in these reactions are poorer. For instance, 1-adamantanol is oxidized to 1,3-adamantane-diol in 43% yield. Secondary alcohols are converted to the corresponding ketone. This method has been employed for the hydroxylation of tertiary positions in saturated acetates and bromides. 

It is clear then that more than one mechanism is operative for glycol fission. In the case of c -cyclopentanediols and camphanediols a cyclic ester is a necessary intermediate. For tra/js-decalin-9,10-diol a non-cyclic mechanism must operate which cannot function for cholestane-3/ ,6j8,7a-triol and is inefficient for /rans-camphanediols. It is pertinent that while the fission of glycols capable of forming cyclic esters proceeds several hundred times faster in benzene than in acetic acid, the reactions of trans-decalin-9,10-diol and tra/ij-hydrindane-l,6-diol are 4-5-fold slower in benzene . ... 

Dehydration. Cu(OTf)2 (0.1 equiv.) is an effective catalyst for dehydration of primary, secondary, or tertiary alcohols and of diols at 25°. The alcohol can be used neat or as a suspension in decalin or heptane. Yields are generally higher than those obtained with H2S04 or POCl3/pyridine. Saytzeff (E)-alkenes are formed predominantly. 

The acetonation under kinetically controlled conditions is also useful for the protection of vicinal rra/u-diols, which are quite reluctant to cyclization into five-membered rings. Although use of 2-methoxypropene has been successful in this objective [61,66], one should recommend the recently discovered uses of reagents that minimized the ring strain by obtaining six-membered rings from vicinal mmr-dials, which are protected (Scheme 10) as 1,4-dioxanes (dispiroacetals, rranr-decalinic system) stabilized by an anomeric effect... 

Rates of losses of water from the molecular ions of stereoisomeric decalin-1, 4-diols have been reported [349]. 

Payne and Smith59 studied the hydroxylation of cyclohexene with a mixture of 34% hydrogen peroxide and a little tungstic acid in acetone. In addition to trans-1,2-cyclohexanediol, they obtained a 25% yield of 3,3-dimethyl -1,2,4-trioxaacetone derivative of the intermediate hydroxyhydroperoxide. Hydrogenation of 71 leads to tm w-cyclo-hexane-l,2-diol. 

A catalytic bismuth system (Ph3Bi-NBS-K2C03-MeCN with 1% water) has been reported to cleave a range of 1,2-glycols efficiendy and is shown to have a different mechanism from the cyclic process observed with the stoichiometric bismuth reagent (2). The catalytic system cleaves cis and rra/i -decalin-9,10-diols at nearly the same rate, whereas the stoichiometric reagent (2) does not cleave the trans... 

Johnson et al. ° prepared rra s-decalin-l,4-dione by hydrogenation of 1,4-naphthoquinone over RUO2, followed by chromic acid oxidation of the resulting diol and isomerization of the cis- to the rrnn.v-dione. 

A new synthesis of nojigiku alcohol (773) (Vol. 4, p. 554) starts from tricyclene (774) and we should perhaps recall the preparation of the latter from camphor (40) tosylhydrazone and sodium methoxide in decalin. [Tricyclene is also produced in other reactions leading to camphene (775), such as the reaction of 3-bromocamphor with methylaniline. ] TTie new synthesis consists in anodic oxidation with triethylamine in acetic acid, and yields 76% of 773, with 8% of the endo-isomer and 11% of diols. Oxidation of tricyclene (774) with lead tetraacetate also gives nojigiku alcohol (773), but as a minor (16%) product, the main product being camphor (40). Tricyclene having a plane of symmetry, these methods all lead to racemic 773. 

Intramolecular acylation. This reaction is the key step in a new synthesis of the twistane ring system By a Canadian group.14 The starting material, decalin-2,7-dione (3), can be prepared easily in quantity by hydrogenation of 2,7-dihydroxynaphthalene to a mixture of isomeric diols (2) and chromic acid oxidation of the mixture.15 16 Treat-... 

Oxidation of benzylidene acetals. Deslongchamps has extended his studies on ozonization of acetals to benzylidene acetals. Ozonization of the benzyhdene derivatives (1) of 9/3,lOa-decalin-20,3 -diol in acetic anhydride containing sodium acetate results in formation of a single product (2) with an axial benzoate group and an equatorial acetate group. This is the same isomer that is obtained from the hemiortho ester (3) thus (3) or an equivalent substance is a probable intermediate in the ozonolysis of (1). 

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