Spiro nonane-1,6-dione

Nearly all examples of epoxidation of alkylidenecyclobutanes involve 3-chloroperoxybenzoic acid.15 58-70 This is because the conditions are mild, the workup is easy and few byproducts are formed. Generally, dichloromethane or chloroform is used as solvent. Solid sodium hydrogen carbonate is occasionally added to avoid acid-catalyzed rearrangement of the spiro compound. For example, 6-isopropylidene-l,4,4-trimethylbicyclo[3.2.0]heptan-3-one reacted with 3-chloroperoxybenzoic acid and sodium hydrogen carbonate to give 2,2,3, 3, 6-pentamethyl-spiro[3-oxabicyclo[4.2.0]octane-8,2 -oxirane]-4-one (4) in quantitative yield. However, without the use of sodium hydrogen carbonate, substantial amounts of 2,2,6,9,9-pentamethyl-3-oxa-bicyclo[4.3.0]nonane-4,8-dione (5) and 2,2,6,8,8-pentamethyl-3-oxabicyclo[4.3.0]nonane-4,9-dione (6) were also formed.15-64... 

The absolute configuration of (-)-spiro[4.4]nonane-l,6-dione was determined by application of Horeau s method of optical rotations.[45] In support of the assignment, and with greater certainty, the Exciton Chirality Rule was applied to the bis-p-dimethylamino-benzoate of the cis,trans-diol obtained following reduction of the diketone. The cis,trans-diol is readily distinguished by NMR from the C2-symmetry cis,cis and rrans,rrans-diols. Since the cis,trans-diol dibenzoate from the (-)-dione exhibits a (-) exciton chirality CD, it follows that the absolute configuration of the dione is that shown in Figure 37. The absolute stereochemistry is easily determined by CD. 

Figure 37. (a) Formation of the ds,trans-diol of (-)-spiro[4.4]nonane-l,6-dione. (b) Observed CD of the bis-p-dimethylaminobenzoate of the cis,trans-diol. (c) Exciton chirality. 

Other possible cases of chiral tetracoordinate centers exist beside the asymmetric centers (point group C,) discussed above. Indeed, chiral molecules of higher symmetry exist these may contain a chiral center of the types Z(a2b2) (point group C2), Z(a3b) (point group C3), or Z(a4) (point group D2). An example of C2 chirality is provided by (S)-( — )-spiro[4.4]nonane-l,6-dione (XVI) [33]. An in-depth discussion... 

Optical Resolution. This reagent is commonly used for the optical resolution of various compounds. Racemic spiro[4.4]nonane-1,6-dione was the first compound to be resolved (55% overall yield). The corresponding semioxamazone was obtained in optically active pure form in two or three recrystallizations and hydrolyzed to (—)-(5)-spiro[4.4]nonane-l,6-dione in a refluxing methanol-water mixture in the presence of Iodine (eq 2). 

Under the same conditions. (4, spiro[4.4]nonane-1,6-dione) is obtained from (3) in 81 % yield. 

Spiro[4.4]nonane-1,6-diol, 343 Spiro[4.4]nonane-l,6-dione, 396, 397 Spiro[4.4]nonatetraene, 357-358 Spiro[4.4 ] nona-1,3,7-triene, 457... 

Phenylpropane-l,2-diols, A21.1, A21.2, A"16 Spiro[4.4]nonane-l, 6-dione, X 3.9 Norbornenecarboxylic acids, methyl esters,... 

Several aliphatic or aromatic diols were employed for the construction of the backbone, such as l-benzyl-3,4-dihydroxypyrrolidine-2,5-dione, enan-tiopure binaphthols or achiral biphenols, brenzcatechol, aliphatic diols, or spiro[4.4]nonane-1.6-diol (see also Section 2.2.2) [44-47]. Three-carbon bridged diols proved to be more effective compared to two-carbon or four-carbon bridged analogs, which has been explained by a counterproductive fluxional behavior in the corresponding rhodium complexes [48]. Diphosphites based on 1,3-diphenylpropane also produced iirferior enantioselectivities in comparison to the 2,4-pentanediol backbone of Chiraphite. For the design of both side arms, it was concluded that a diphosphite based on the unsubstituted biphenol is less suited... 

Norbomenecarboxylic acids, methyl esters, A47.il Spiro-[4.4]-nonane-l,6-dione, X 3.9 Allethrolone, T17.10 Bicyclo[3.3. l]nonane-2,6-dione, A 33.2... 

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