Oxirane reactions with alcohols

Nucleophilic Ring-opening Reactions of Oxirans.—Reactions with Oxygen and Nitrogen Nucleophiles. A series of papers have appeared that deal with the reactions of lower aliphatic alcohols (R OH) with (120 = Me) to yield (121 ... 

The ring-opening process of Equation 8.45 is, of course, simply the reverse of the process by which oxiranes (oxacyclopropanes, epoxides) are formed from halohy-drins (e.g., see item 3,Table 7.6). Further, as written, the processes shown in Schemes 8.90-8.92 are reversible and thus, at least in principle, carbonyl compounds can be converted to enol ethers, acetals (and ketals), and orthoesters. However, while acetals and ketals readily form from alcohols and acids under dehydrating conditions (Chapter 9) and esters undergo exchange reactions with alcohols in the... 

The commonest of these for oxirane opening are amines and azide ion [amide ions promote isomerization to allylic alcohols (Section 5.05.3.2.2)]. Reaction with azide can be used in a sequence for converting oxiranes into aziridines (Scheme 49) and this has been employed in the synthesis of the heteroannulenes (57) and (58) (80CB3127, 79AG(E)962). 

Reaction with selenophenoxide ion is one step in a method of converting oxiranes to allylic alcohols under mild conditions (Scheme 51) (73JA2697) (c/. Sections 5.05.3.2.2 and 5.05.3.4.3(/)). 

Substitution of an additional nitrogen atom onto the three-carbon side chain also serves to suppress tranquilizing activity at the expense of antispasmodic activity. Reaction of phenothia zine with epichlorohydrin by means of sodium hydride gives the epoxide 121. It should be noted that, even if initial attack in this reaction is on the epoxide, the alkoxide ion that would result from this nucleophilic addition can readily displace the adjacent chlorine to give the observed product. Opening of the oxirane with dimethylamine proceeds at the terminal position to afford the amino alcohol, 122. The amino alcohol is then converted to the halide (123). A displacement reaction with dimethylamine gives aminopromazine (124). ... 

The oxirane ring opening reaction with alkynyllithiums is of considerable synthetic value, as stereodefined homopropargylie alcohols can be obtained. The lithium acetylide ... 

Similarly, the epoxide (72), on reaction with BH3/UBH4, acetic acid or BC13 gave the tetrahydrothiophene derivatives (74a-c), presumably via the intermediate (73), unlike the analogous cyclohexyl and N-alkylpiperidyl compounds, in which the oxirane opened to give only the expected alcohols (equation 21) (75CPB2701). 

Catalytic amounts of tin(II) chloride have been found to give good yields (72-86%) of the trans-amino alcohols when oxiranes have been treated with aromatic amines in acetonitrile at room temperature.27 Only the reaction with styrene oxide was regiospe-ciflc with the amine adding to the benzylic carbon of the epoxide ring. 

It seems that the initiation step of the copolymerisation most likely involves the oxirane reaction [according to scheme (3)]. Zinc alcoholate species formed in this reaction can easily propagate the copolymer chain, coordinating and enchaining both the oxirane [scheme (3)] and the cyclic carbonate [scheme (15)] comonomers. However, in the case of the cyclic carbonate, its enchainment may also proceed according to scheme (14), leading to decarboxylation. Thus, the obtained poly(ether-carbonate)s are characterised by a lower content of carbonate units with respect to the ether units [82,146]. 

As discussed in section 4, reaction of the peroxy radicals with N02 gives thermally unstable peroxy nitrates. Reaction with H02 gives hydroperoxides and possibly carbonyl compounds. Reaction with other peroxy radicals (R 02) gives alkoxy radicals, carbonyls, and alcohols. The alkoxy radicals will then either isomerize, react with 02, or decompose (see Sect. 3). Thus, the NO3 radical-initiated atmospheric degradation of alkenes leads to oxiranes (generally in small yield), nitrooxy hydroperoxides, nitrooxy carbonyls, and nitrooxyalcohols. For a detailed listing of products from individual alkenes the reader should consult Calvert et al. [55]. 

Barton oxidation was the key to form the 1,2-diketone 341 in surprisingly high yield, in order to close the five-membered ring (Scheme 38). The conditions chosen for the deprotection of the aldehyde, mercuric oxide and boron trifluoride etherate, at room temperature, immediately led to aldol 342. After protection of the newly formed secondary alcohol as a benzoate, the diketone was fragmented quantitatively with excess sodium hypochlorite. Cyclization of the generated diacid 343 to the desired dilactone 344 proved very difficult. After a variety of methods failed, the use of lead tetraacetate (203), precedented by work performed within the stmcmre determination of picrotoxinin (1), was spectacularly successful (204). In 99% yield, the simultaneous formation of both lactones was achieved. EIcb reaction with an excess of tertiary amine removed the benzoate of 344 and the double bond formed was epoxidized with peracid affording p-oxirane 104 stereoselectively. Treatment of... 

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