Cyclic ethers reaction with

The hydrosilane-CO combination also brings about unique reactions with cyclic ethers and aldehydes. The former reaction gives silyl ether of w-hydroxyaldehyde ... 

Copper-catalyzed dehydrogenative cross-coupling reactions of (benzo) thiazoles with cychc ethers 106 to give the products 107 have been developed by Jiang and Chen (Scheme 51) (20120L4950, 20130L4600). A radical pathway was proposed for the reaction with cyclic ethers initiated... 

Reaction with Cyclic Ethers. Ring opening of epoxides, ox-etanes, and tetrahydrofurans with phenyl trimethylsilyl selenide... 

A 1 2 mixture of trimethylsilyldiethylarnine and methyl iodide acts as a synthetic equivalent of trimethylsilyl iodide in reactions with cyclic ethers to afford ring-opened a-iodo-< -siloxyalkanes in good yield (eq 6) ... 

However, for a variety of reasons it seems extremely unlikely that the same mechanism is applicable to the polymerisation of cyclic formals and acetals. One reason is that these compounds cannot be co-polymerised with cyclic ethers another is that the polymers are predominantly cyclic, with the number of end-groups far smaller than the number of growing chains. One mechanism which has been proposed and which accounts for most of the observations involves formation of an oxonium ion (X) from the initiator and the monomer, and a subsequent propagation by a ring-expansion reaction (see 13). 

Moriarty, J., Sidebottom, H., Wenger, J., Mellouki, A., and Le Bras, M. Kinetic studies on the reactions of hydroxyl radicals with cyclic ethers and aliphatic diethers, J. Phys. Chem. A, 107(10) 1499-1505, 2003. 

Chiral l,3-dioxin-4-ones photochemically react intermolecular with (cyclic) ethers, acetals, and secondary alcohols to give the addition products in reasonable yields. The radical addition was completely stereoselective at C-6 of the heterocycle <1999EJO1057>. The exocyclic diastereoselectivity, where relevant, was about 2 1 (Equation 30). In analogy, an intramolecular cascade reaction of a 1,3-dioxin -one derived from menthone was used to get a terpenoid or a steroid framework in optically active form <1997JA1129, 1999JA4894>. 

Reaction of Grignard reagents with cyclic ethers... 

Scheme 8.7 Reaction of cyclic ether monomers with trans-(salen)CrXj derivatives.

As an extension of this highly enantioselective Michael addition of silyl nitronates with a, p-unsaturated aldehydes, the reactions with cyclic a,p-unsaturated ketones as a Michael acceptor were also tested (Scheme 9.15). Cyclohexenone and cyclohepte-none were employed as a useful Michael acceptor with various silyl nitronates in the presence of catalyst (R,R)-6c, and gave the corresponding enol silyl ethers 28 with excellent stereoselectivities [30]. 

Scheme 7.15 Stereoselectivity of the PB reaction of cyclic ethers with benzaldehyde.

Bromotrimethylsilane reacts with lactones884, with cyclic ethers, particularly oxiranes, and with secondary and tertiary ethers885 to yield brominated products. The reaction is catalyzed by IBr (equation 128)886. 

To make ethers more reactive, they must be complexed with strong Lewis acids. BF3 is commonly used with cyclic ethers, and even with epoxides it increases the rate and yield of the reaction when organometallic reagents are used as nucleophiles. BF3 is most easily handled as its complex with diethyl ether, written BF3 OEt, BuLi does not react with oxetane, for example, unless a Lewis acid, such as BF3, is added, when it opens the fouremembered ring to give a quantitative yield of H-heptanoI. 

HDA reactions with cyclic enol ethers, treatment of which with NH4OAC gives 3-(2-hydroxy-benzoyl)pyridines <07TL6297>. 

As the hydrosilation reaction is related to hydrogenation, it also bears a certain relationship to the hydroformylation (see Hydroformylation) reaction. The Co2(CO)g catalyzed process, which formylates an alkene in the presence of a hydrosilane instead of hydrogen, gives silyl enol ethers in excellent yields (equation 27). The hydrosilane/CO system can also react with cyclic ethers or aldehydes to give co- or... 

In contrast, the reactions of iododiorganophosphines with cyclic ethers lead to the related phosphoryl halide and an alkene... 

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