Chloroalkyl epoxides

In addition to the enzymatic hydrolysis of esters, there also ample examples where an epoxide has been cleaved using a biocatalyst. As described by the Faber group [19], reaction of the ( )-2,3-disubstituted ds-chloroalkyl epoxide roc-8-40 with a bacterial epoxide hydrolase (BEH), led to the formation of vie-diol (2 ,3S)-8-41 (Scheme 8.11). The latter underwent a spontaneous cydization to give the desired product (2i ,3i )-8-42 in 92 % ee and 76 % yield. The same strategy was used with the homologous molecule rac-8-43, which afforded the THF derivative (2R,3R)-S-4S in 86% ee and 79% yield. 

P-Ghloroalkoxy Titanates. The reaction of TiCl with epoxides, such as ethylene or propylene oxide (qv), gives P-chloroalkyl titanates (8,9). One example is Ti(OCH2CH2Cl)4 [19600-95-5]. The P-chloroalkoxy titanates can be used to biad refractory powders and ia admixture with diethanolamine to impart thixotropy to emulsion paints (10). 

Nitrosyl chloride and dinitrogen tetroxide. Malinovaku and co-workers10 8 published in I .r>3 an interesting study of the addition of xiitroayl chloride to several epoxides to give /S-chloroalkyl nitrites Eq. 938). 

Asymmetric induction occurs during the alkylation of ketones with the a-sulfinyl carbanion derived from optically active 1-chloroalkyl-p-tolyl sulfoxides (equation 18). The resulting chloro alcohol may be converted to an optically active epoxide under alk ine conditions and the sulfinyl group is removed with n-butyllithium. While the process benefits from high asymmetric induction in the alkylatitm reaction, it must be recognized that, when either R 91H and/or R R diasteretHnerk compounds are formed and require separation. 

The current product range of developmental samples covers monofunctional fluids of aminoalkyl, chloroalkyl, vinyl, and (meth)acryloyl types. Molecular mass is 1700 and 4000 Da, and product viscosities reach from 15 to about 80 mPas. The appearance of the fluids is optically clear and colorless to slightly amber. Technologically accessible future fimctionalities include caibinol, epoxide, substituted phenyl, hydrosilyl, caiboxy, sulfhydtyl, polyglycol, and other groups (see literature attached). In Fig. 2, currently available products are sketched. 

Sulfoxide-magnesium exchange on the a-chloroalkyl sulfoxide 42 was performed with ethylmagnesium bromide followed by trapping with benzaldehyde-dimethyl-aluminum chloride, to furnish 99% of the sulfoxide 43 with 99% ee. Chlorohydrins 44 were obtained in 56% yield as a 94 6 diastereomer mixture. After conversion to the epoxide 45, the latter had an ee of >98% (Scheme 3.18). 

P-Chloroalkyl esters. These reagents enable transformation of epoxides to /3-chloroalkyl esters without simultaneous generation of HCl therefore, potentially sensitive compounds (acrylate, etc.) are prepared cleanly. The silica-linked hexa-butylguanidinium chloride is particularly effective. 

The Grignard reagents of (chloroaIkyl)(isopropo3gr)dimethylsilane (42, R -O-iPr) and (chloroalkyl)(dimethyl)phenylsilane (43, R = Ph) provide excellent hydroxyallqrl anion equivalents, which react with electrophiles such as aldehydes, imines, ] ketones and epoxides to give the adducts 44 and 45, respectively (Scheme 14). The hydroxyalkyl group 46 is revealed using the standard silyl-to-hydroxy protocols. 

Darzens reactions of aromatic aldehydes and a-chloroacetonitriles, oc-chloroalkyl sulfones, or phenacyl halides with ephedrine or quinine derivatives as catalysts afforded epoxides in low optical yields... 

The siloxane sequences containing these ends have been joined to other polymeric sequences such as carbonates, ureas, urethanes, amides, and imides. Other functional groups include amines and sulfonic acids, ° ° ammonium groups, epoxides, and chloroalkyl groups. ... 

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