Boron trifluoride oxetane

The acid-catalyzed reaction of oxetanes with t- butyl isocyanide gives 2-iminotetra-hydrofurans, boron trifluoride etherate being used as catalyst (equation 26). The authors proposed that the isocyanide reacts with the protonated oxetanes by an N2 mechanism (70S475). 

The synthesis of AMO involves treatment of 3,3-bis(chloromethyl) oxetane (BCMO) with sodium azide in the DMF medium at 85 °C for 24 h. Similarly, AMMO which is a monofunctional analog of AMO is synthesized by the azidation of chloro/tosylate product of 3-hydroxymethyl-3-methyl oxetane (HyMMO) with sodium azide in DMF medium at elevated temperatures. These energetic monomers are readily polymerized to liquid curable prepolymers with the help of boron trifluoride etherate/l,4-butanediol initiator system and the outlines of synthesis [147-150] of poly(BAMO) [Structure... 

No reaction occurred when trifluorovinyllithium was treated with epoxides or oxetanes, but with boron trifluoride catalysis the corresponding trifluorovinyl-ated alcohols were obtained in good yields [119] (Scheme 43). 

The ring expansion of 2-f-butyloxetanes to tetrahydrofurans in the presence of a Lewis catalyst has been reported. Treatment of the oxetane (341) with boron trifluoride etherate in diethyl ether leads to the ring expanded product (342). It is suggested that an intermediate carbocation is formed (Scheme 92) (79CC382). 

Diones are normally synthesized from /3-hydroxy acids in two steps first, conversion into carbamates by reaction with sodium cyanate, and then cyclization with thionyl chloride (Scheme 103) (54JCS839). Alternative preparations utilize oxetanes, which may be combined either with isocyanates in the presence of boron trifluoride (68JAP6808278) or with S-alkylthioureas (Scheme 104) (69ZOR1844). In the last example the initial products are imines (224) which may readily be hydrolyzed to the required diones. Similar methods can be applied to the synthesis of tetrahydro-l,3-thiazine-2,4-diones, and, for instance, the 4-oxo-2-thioxo derivative (225) is obtained from /3-propiolactone and dithiocarbamic acid (Scheme 105) (48JA1001). 

Phenyl trimethylsilyl telluride, 248 Tetrabutylammonium iodide-Boron trifluoride etherate, 287 of oxetanes... 

Oxetanes having ether groups in a side chain (21) undergo rearrangement in the presence of boron trifluoride etherate to give... 

Resin-based chemistry has been used to construct 480 from 481 by use of boron trifluoride to mediate both the cyclization and cleavage steps <1999AGE1121 >. When the monosaccharide was bound to the polystyrene resin (Merrifield and MPP type) by an alkylsulfonyl linker 482 and cyclization was mediated by 2- r/-butylimino-2-diethylamino-l,3-dimethylperhydro-l,3,2-diazaphosphorine, the reaction had low stereoselectivity and the products included tricyclic oxetanes and oxiranes <2004EJ04177>. The Mitsunobu reaction was used to obtain intramolecular N-alkylation of 483 and formation of 484 <2005AGE3732>. 

Oxetanes Boron trifluoride. Cobalt meso-Tetrapheny Iporphine. 

Yamaguchi and Hirao found that alkyneboron difluorides, which are prepared from the alkynide ion and boron trifluoride etherate, react with oxiranes to give the 2-alkynols (Scheme 15). The same research group also found that ring opening of oxetane could be accomplished, but in this case boron trifluoride had to be added as a Lewis acid (Scheme 15). 

The most versatile method involves rearrangement of an acylated hydroxymethyloxetane catalyzed by boron trifluoride etherate (13. 17). The triols are readily converted to the required hydroxymethyl oxetanes via pyrolysis of the carbonate esters (18) and then to the acylated hydroxymethyloxetanes with acid chlorides. 

Epoxides and oxetanes possessing ether substituents in the side chain rearrange in the presence of boron trifluoride etherate to form ring enlarged cyclic ethers <94H(38)2I6S>. By the appropriate selection of side chain the method may be used to form oxepanes bearing 3-CH2-0-alkyl(or alkenyl) substituents. 

Derivatives of azete are only known as unstable reaction intermediates. Oxetane and azetidine are considerably less reactive than their three-membered counterparts (oxetane reacts with hydroxide anion 10 times more slowly than does oxirane), but nonetheless do undergo similar ring opening reactions for example, oxetane reacts with organolithium reagents, in the presence of boron trifluoride, or with cuprates, and azetidine is opened on heating with concentrated hydrochloric acid. 

Theoretically, any Lewis acid can catalyze oxetane polymerizations. However, these acids differ considerably in their effectiveness. Boron trifluoride and its etherates are the most widely reported catalysts. Moisture must be excluded as it tends to be detrimental to the reaction. " ... 

It was reported that when oxetane polymerizations are carried out with boron trifluoride catalyst in methylene chloride at temperatures between 0 °C to -27.8 °C, a cocatalyst is not required. The product, however, is a mixture of a linear polymer and a small amount of a cyclic tetramer. This is in agreement with an earlier observation that the polymerizations of oxetane are complicated by formations of small amounts of cyclic tetramers. Other catalysts, protonic acids, capable of generating oxonium ions, will polymerize oxetane. These acids are sulfuric, trifluoracetic, and fluorosulfuric. The initiation reaction can be illustrated as follows ... 

MeOTf has been reported to effect the dealkoxylation of a perfluoroalkyltrialkoxyboronate to generate the corresponding boronic ester, l Conversely, an alkenyl boroxycarbene complex was reacted with MeOTf to remove the borane-based chiral auxiliary yielding a Fischer carbene complex. l l ferf-Amide substituted oxetanes rearranged in anhydrous nitrobenzene at 150 °C with a catalytic amount of MeOTf to produce ester-substituted azetidines (eq 16).i Other acids such as boron trifluoride ether-ate, trifluoromethanesulfonic acid, and benzylthiolanium hexaflu-oroantimonate led to low yields of the desired azetidines. 

A new class of 110-nitro-9a-hydroxyestrogens was preparej by treating 3-acetoxy-l,3,5(10),9(ll)-estratetraen-17-one with nitric acid. The treatment of cholest-4-en-3-one with t-butyl isocyanide followed by boron trifluoride afforded a class of oxetane alkyidiimines represented by 6, ... 

The polymerization o oxetanes with cationic catalysts has been studied by many investigators. (1.H2) RoseC. ), in particular, first reported the homopolymerization of the parent compound, tri-methylene oxide (TMO), with a Lewis acid catalyst, boron trifluoride. The use of coordination catalysts to polymerize oxetanes has been reported in the patent literature by Vandenberg.W In this work, Vandenberg polymerized oxetanes with the aluminum trialkyl -water-acetylacetone coordination catalyst (referred to as chelate catalyst) that he discovered for epoxide polymerization . This paper describes the homo- and co-polymerization of TMO with these coordination catalysts. Specific TMO copolymers, particularly with unsaturated epoxides such as allyl glycidyl ether (AGE), are shown to provide the basis for a new family o polyether elastomers. These new elastomers are compared with the related propylene oxide-allyl glycidyl ether (PO-AGE) copolymer elastomers. The historical development and general characteristics of polyether elastomers and, in particular, the propylene oxide elastomers, are reviewed below. 

The ring-opening polymerizations of oxetanes (1,3-epoxides) with Lewis acids such as boron trifluoride etherate and aluminum alkyls are well documented. Hall and coworkers reported the ring-opening polymerization of 7-oxabicyclo[2.2.Ijheptane (50) with Lewis acids such as boron trifluoride etherate to give poly(cyclohexene oxide) (51). Ogata reported that the polymerization of... 

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