Synthesis by Halohydrin Cyclizations and Related Reactions

Synthesis of Oxirans by Halohydrin Cyclizations and Related Reactions. One of the oldest commercial methods for the production of ethene oxide is the chlorohydrin route, involving chlorohydration of ethene followed by dehydrochlorination. An improved procedure for the second stage of this process has been reported in which a basic ion-exchange resin is used to 

Sagami Chemical Research Center, Jpn. Kokai Tokkyo Koho 82 26 677. K. S. Bhat and A. S. Rao, Indian J. Chem., Sect. B, 1981, 20, 355. 

Synthesis of Oxirans via Attack of a Carbanion on the Carbonyl Group of Aldehydes and Ketones. The dibromo-ketones [34 R = 4-MeC6H4, 

The sulphonium ylides (42 R = R R C=CHCH2 or R CH2), derived from tetrahydrothiophen, have been used for the synthesis of the halogenated vinyl epoxides [41 R R = Br, Cl, or H (however, either R or R must be halogen) R = H, Me, Me2CH, MeCH=CH, H2C=CMe, Me2C=CH, Ph, or PhCH=CH] (23-87%) by reaction with the appropriate aldehydes. The more complex salt (43), on reaction with HCO(CH2)3COOMe, gave the (/ , 5 )-(all- )-epoxide (44) as a mixture of cis- and rraws-isomers 

The first examples of reactions of non-stabilized selenium ylides with enolisable carbonyl compounds have been reported. Ylide (45) was generated in situ from Me2 ePh MeS04 and NaH in the presence of R COR [R = Ph, 4-O2NC6H4, Bu, or hexyl R = H, Me, or Et or R R = (CH2)s] to give the corresponding oxirans (76-94%).  

---