Cyclic 1,3-diol derivatives

The great utility of fragmentations, especially those of 1,3-diol monosulfonates, for the construction of functionalized, medium-sized cycloalkenes was developed by Wharton, by applying previous results. In recognition of his important contributions to the chemistry of heterolytic fragmentations of cyclic 1,3-diol derivatives, this reaction type has been referred to in a recent review as the Wharton fragmentation . ... 

Caine, D. Wharton fragmentations of cyclic 1,3-diol derivatives. A review. Org. Prep. Proced. Int. 1988, 20, 1-51. 

Ebelman and Bouquet prepared the first examples of boric acid esters in 1846 from boron trichloride and alcohols. Literature reviews of this subject are available. B The general class of boric acid esters includes the more common orthoboric acid based trialkoxy- and triaryloxyboranes, B(0R)3 (1), and also the cyclic boroxins, (ROBO)3, which are based on metaboric acid (2). The boranes can be simple trialkoxyboranes, cyclic diol derivatives, or more complex trigonal and tetrahedral derivatives of polyhydric alcohols. Nomenclature is confusing in boric acid ester chemistry. Many trialkoxy- and triaryloxyboranes such as methyl, ethyl, and phenyl are commonly referred to simply as methyl, ethyl, and phenyl borates. The lUPAC boron nomenclature committee has recommended the use of trialkoxy- and triaryloxyboranes for these compounds, but they are referred to in the literature as boric acid esters, trialkoxy and triaryloxy borates, trialkyl and triaryl borates or orthoborates, and boron alkoxides and aryloxides. The lUPAC nomenclature will be used in this review except for relatively common compounds such as methyl borate. Boroxins are also referred to as metaborates and more commonly as boroxines. Boroxin is preferred by the lUPAC nomenclature committee and will be used in this review. 

Meso Compounds. Although pig liver esterase is by far the most suitable enzyme for asymmetric transformations involving meso compounds, especially diacids, there are several reports on the lipase-catalyzed hydrolysis and transesterification reactions of cyclic diol derivatives. The former includes variously substituted cycloalkene diacetates, cyclohexylidene protected erythri-tol diacetate, piperidine derivatives, and the exo-acetonide in eq 11. Complementary results are clearly demonstrated in eq 11 and eq 12 for the hydrolysis and esterification processes. 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

A variety of cyclic ortho esters,including cyclic orthoformates, have been developed to protect czs-1,2-diols. Cyclic ortho esters are more readily cleaved by acidic hydrolysis (e.g., by a phosphate buffer, pH 4.5-7.5, or by 0.005-0.05 M HCl) than are acetonides. Careful hydrolysis or reduction can be used to prepare selectively monoprotected diol derivatives. 

The catalytic enantioselective desymmetrization of meso compounds is a powerful tool for the construction of enantiomerically enriched functionalized products." Meso cyclic allylic diol derivatives are challenging substrates for the asymmetric allylic substitution reaction owing to the potential competition of several reaction pathways. In particular, S 2 and 5n2 substitutions can occur, and both with either retention or inversion of the stereochemistry. In the... 

Cyclic acetals derived from diols and o-nitrobenzaldehyde produce hydroxynitrosobenzoates upon irradiation (see Scheme 26). Early studies of this reaction demonstrated that acetals involving carbohydrates and o-nitrobenzaldehyde experience facile, photochemical... 

Acyloin condensation of diester 30a with sodium in liquid ammonia, followed by direct hydrogenation in the presence of Adam s catalyst, furnished the diol 32 in 49% yield. Diol 32 was transformed into the cyclic thiocarbonyl derivative (80% yield) which after heating with trimethylphosphite [14] afforded twistene 33 in 50% yield. Hydrogenation of 33 gave a compound identical in all respects with twistane 1. From the diester (-)-30a (+)-twistene was obtained, m.p. 35.5-36.5 °C, +... 

Although the presence of BINOL in the ligands so far discussed has shown itself to be particular effective, modification of the diol moiety provides new classes of ligands for this addition reaction. Alexakis, screening a number of chiral phosphites in the Cu(OTf)2-catalyzed 1,4-addition, showed that an ee of 40% could be obtained for the addition of Et2Zn to 2-cyclohexenone and of 65% for addition to chalcone, by using cyclic phosphites derived from diethyl tartrate [51]. 

A new class of functional comonomers exemplified by acrylamidobutyraldehyde dialkyl acetals 1 and their Interconvertible cyclic hemlamidal derivatives 2 were prepared and their chemistry was Investigated for use In polymers requiring post-crosslInking capability. These monomers do not possess volatile or extractable aldehyde components and exhibit additional crosslinking modes not found with conventional am1de/forma1dehyde condensates, eg, loss of ROH to form enamides 9 or TO and facile thermodynamically favored reaction with diols to form cyclic acetals. 

The stereochemical outcome of the cycloaddition to 3-butene-1,2-diol derivatives, cyclic acetals, or to related alkenes that possess an allylic nitrogen substituent such as 4-vinyl-oxazolines or -oxazolidines was also rationalized by this model (162) (Table 6.7). In the latter cases, the A-Boc group instead of the a-oxygen prefers the inside position (Scheme 6.24). 

Molecules with Two or More Functional Nonchromophoric Groups 4.4.2.4.I. Derivatives of Cyclic Diols and Polyols... 

Predicted and observed 31P NMR spectra of the mixtures of syn and anti cyclic triesters derived from labeled samples of 1 phospho-(S)-propane-l/2-diols that are R and S at phosphorus. 

The reaction is highly regioselective for substituted cyclic ortho esters, with ring opening mainly at the primary carbon center. However, reversed reactivity is observed for the phenyl-substituted derivative. Corresponding 1,4- and 1,5-diol derivatives are obtained in reaction of six- and seven-membered cyclic ortho esters. 

Treatment of diethyl malonate and related compounds with 1,2-dihaloethane in the presence of base constitutes a classical method of cyclopropane synthesis296"300. The reaction can be conveniently carried out under PTC conditions. An improved method utilizing solid-liquid phase transfer catalysis has been reported298. The reaction of dimethyl or diethyl malonate with 1,2-dibromoalkanes except for 1,2-dibromethane tends to give only low yields of 2-alkylcyclopropane-l, 1-dicarboxylic esters. By the use of di-tm-butyl malonate, their preparations in satisfactory yields are realized (equation 134)297. The 2-alkylcyclopropane derivatives are also obtained from the reaction of dimethyl malonate and cyclic sulfates derived from alkane-1,2-diols (equation 135)301. Asymmetric synthesis... 

Cyclic orthoesters derived from gem-diols offer a further route to alkenes. As part of a three-step conversion, they may be ring opened with hydrobromic acid to give O-acyl bromodeoxy compounds that undergo reductive elimination with copper-zinc. In this way, unsaturated nucleosides have been made by way of mixed 2y3,-bromo-2y3,-deoxy-3,/2, carboxyl-ates.174 A more direct route to alkenes from cyclic orthoesters involves heating in acetic anhydride together with zirconium oxide.175... 

Brunelle et al. [157] developed high-yielding syntheses of cyclic esters derived from 1,4-aromatic acyl chlorides and diols. Hodge et al. [158] used a solid support and step growth polymerization to produce a polyester chain followed by treatment with a metal catalyst, most often Bun2SnO, to affect intrachain transesterification and release of the cyclic esters into the solution phase. 

One of the first effective chiral PPY derivatives to be developed for asymmetric acyl transfer was catalyst 7, which was shown by Fuji and Kawabata in 1997 to be effective for the acylative KR of various racemic mono-benzoylated ds-diol derivatives [76]. Subsequently, it was also successfully applied in the KR of N-protected cyclic ds-amino alcohols [77]. Using 5 mol% of PPY 7 in the presence of a stoichiometric amount of collidine in CHCI3 at rt, a variety of cyclic ds-amino alcohol derivatives were resolved with moderate selectivities (s = 10-21) (Table 8.6). 

Cyclic thiocarbonates offer another class of substrates for radical deoxygenation (Scheme 3.9b). In particular, thiocarbonates formed from a diol derived from a primary and secondary hydroxyl are of particular interest, since they can be deoxygenated regioselectively with tributyltin hydride and AIBN.53 In these cases, the secondary position is deoxygenated owing to the higher stability of secondary over primary radicals. As expected, radical reduction of thiocarbonates derived from two secondary hydroxyls leads to a mixture of deoxygenated isomers.52b 53... 

However, 1,2-diaddition was observed in the case of a,f)-unsaturated aldehydes and other ketones. The corresponding chalcone adduct 490 has been reduced to compound 491, which was transformed into the cyclic acetal 492 and the 1,4-diol derivative 493. 

Dinitrophenol was used with benzyloxy-bis(diisopropylamino)phosphine 243 to synthesize the cyclic phosphate derivatives 244 of a series of alkane diols (HO-(CH2) -OH n = 4-6) in good isolated yields <2004TL1001>. 

The cyclic (iodomethyl)carbamates 15 can be easily converted into 3-amino-l,2-diol derivatives 17 via iodine displacement with Amberlyst A-26 in the acetate form. In addition, cleavage of the carbon- iodine bond (lithium aluminum hydride or tributyl tin hydride) leads to the trans-2-oxazolidinones 18, which are useful intermediates for the synthesis of 1,2-iyn-amino alcohol systems 199 12. 

The asymmetric transesterification of cyclic me o-diols, usually with vinyl acetate as an irreversible acyl transfer agent, includes monocyclic cycloalkene diol derivatives, bicyclic diols, such as the ej o-acetonide in eq 12, bicyclic diols of the norbomyl type, andorganometallic l,2-bis(hydroxymethyl)ferrocenepossessing planar chirality. 

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