1.3- Dioxane synthesis

Furodysinin hydroperoxide, isolation, 134-5 Fused bicycUc 1,2-dioxanes, synthesis, 196, 197... 

History of the Discovery of the 1,2-Dioxane Synthesis Using Manganese(lll) Complexes... 

The limitation on this simple dioxan synthesis is that unbranched olefins are unreactive. Nevertheless, the method offers advantages over the alternative acid-catalyzed (Prins) reaction in regard to both product yield and selectivity. 

Benzoate. CsHMF06, W 5975, Debate, Beben, Benisone. Euvaderm, Flu robote, Parbetan, Uticort, Crystals from acetone-ether, mp 225-228. [alj,4 +63,5" (dioxane). Synthesis and activity Ercoli et al., J. Med. Chem. 15, 783 (1972). See atso Cullen, Curr. Ther. Res. 15, 243 (1973). 

PRINS KRIEWITZ Hydrexymethylat Acid catalyzed hydroxymethytation o( akenes. 1,3-Dioxane synthesis. 

Zong, K., K.A. Abboud, and J.R Reynolds. 2004. A palladium-catalyzed synthesis of 2-alkylidene-pyrrolo[c]-l,4-dioxanes Synthesis of 3,4-(cis-l,2-dimethyl)ethylenedioxypyrrole. Tetrahedron Lett 45 4973 975. 

The /-butoxycarbonyl group (Boc, "t-box ) has been eMens vely used in peptide synthesis, and Boc derivatives of many amino acids are commercially available. The customary reagent for the preparation from the amine is t-butyl azidoformate in water, dioxane/water, DMSO, or DMF. The cleavage by acids of medium strength proceeds with concomitant loss of isobutene and carbon dioxide (L.A. Carpino, 1957, 1973 see section 4.1.2.2). 

Because coupling is not always quantitative, the non-reacted terminal deoxynucteoside must be excluded from the following synthesis cycles. Otherwise deletion sequences will render the isolation of the pure final product difficult. Therefore a capping step (step 3) follows, e.g., acetylation with acetic anhydride and N,N-dimethyl-4-pyridinamine (DMAP) in dioxane. Capping times should be as short as possible, especially with 2-cyanoethyl phosphite triesters, which are sensitive to bases such as DMAP. 

A commercial process based on the Prins reaction is the synthesis of isoprene from isobutylene and formaldehyde through the intermediacy of 4,4-dimethyl-l,3-dioxane (49—51) ... 

The poly(vinyl alcohol) made for commercial acetalization processes is atactic and a mixture of cis- and /n j -l,3-dioxane stereoisomers is formed during acetalization. The precise cis/trans ratio depends strongly on process kinetics (16,17) and small quantities of other system components (23). During formylation of poly(vinyl alcohol), for example, i j -acetalization is more rapid than /ra/ j -acetalization (24). In addition, the rate of hydrolysis of the trans-2iQ. -A is faster than for the <7 -acetal (25). Because hydrolysis competes with acetalization during acetal synthesis, a high cis/trans ratio is favored. The stereochemistry of PVF and PVB resins has been studied by proton and carbon nmr spectroscopy (26—29). 

Synthesis of 2-thioxopenams (76) has also been realized usiag a [sulfur, C-5] ring closure (117). Cyclization of 4-(3)-chloroazetidinone [88816-44-8] (77, R = R = SCOCH ), C22H22ClN20gS2, usiag imidazole ia aqueous dioxane proceeded stereospecifically to give the 5-(R)-thioxopenam [83362-57-6]... 

Hydrolysis of esters and amides by enzymes that form acyl enzyme intermediates is similar in mechanism but different in rate-limiting steps. Whereas formation of the acyl enzyme intermediate is a rate-limiting step for amide hydrolysis, it is the deacylation step that determines the rate of ester hydrolysis. This difference allows elimination of the undesirable amidase activity that is responsible for secondary hydrolysis without affecting the rate of synthesis. Addition of an appropriate cosolvent such as acetonitrile, DMF, or dioxane can selectively eliminate undesirable amidase activity (128). 

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