Alkali-induced reactions of N-nitrosooxazolidones and N-nitrosoacetylamino alcohols containing cyclopropyl groups

Abstract

The reactions'of 5-cyclopropyl-5-phenyl-3-nitrosooxazolidone (6), 5,5-dicyclopropyl-3-nitrosooxazolidone (7), and 5-cyclopropyI-5-methyl-3-nitrosooxazolidone (8) under alkaline conditions are described. When methanolic solutions of 6 are treated with aqueous hydroxide, about 90% yields of cyclopropylphenylacetylene (9a) are obtained. On similar treatment, 7 yields about 52% dicyclopropylacetylene (9b) together with about 21% 2,2dicyclopropylvinyl methyl ether (10b), and 8 yields only 16% cyclopropylmethylacetylene (9c) together with about 64% a nearly 1:1 mixture of the Z and E forms of 2-cyclopropyl-l-propenyl methyl ether (10c). When a cyclohexene solution of 6 is added to a suspension of lithium ethoxide in cyclohexene, an 84% yield of 9a is obtained. On similar treatment, 7 yields 64% 9b and about 13% 7-(dicyclopropylmethylene)bicyclo[4.1.01heptane (5b), while 8 yields about 26% 9c and 44% 7-(2-cyclopropylpropylidene)bicyclo[4.1.0]heptane (5c). Mechanisms which involve unsaturated carbonium ions and unsaturated carbenes are advanced to explain the results. Treatment of a cyclohexene-pentane solution (containing a small amount of Aliquat, a long chain quaternary ammonium chloride) of 2-(A7-nitrosoacetylamino)-l,l-dicyclopropylethanol ( 17) with 50% sodium hydroxide afforded a 64%¡ yield of 5b. Similar treatments of l-(iV-nitrosoacetylamino)-2-cyclopropyl-2-propanol (18) yielded 52% 5c.The reactions of 5,5-disubstituted-3-nitrosooxazolidones (I) with bases in polar media have been studied.3®

Alkylidenecarbenes, Alkylidenecarbenoids, and Competing Species: Which Is Responsible for Vinylic Nucleophilic Substitution, [1 + 2] Cycloadditions, 1,5-CH Insertions, and the Fritsch−Buttenberg−Wiechell Rearrangement?

“…Of course, this intermediacy of the highly labile 53 implies an open route to alkylidenecarbenes 12. Accordingly, the base-induced "FBW" migration of the cyclopropyl group (R 2 in 96 and perhaps in 12) at room temperature to give cyclopropyl alkynes could compete 107 with the [1 + 2] cycloaddition to cyclohexene and with intermolecular OH insertion into the solvent methanol (producing R 1 R 2 CdCHsOMe with R 2 ) cyclopropyl). On the other hand, alkenyl cations R 1 R 2 CdCH + (rather than 12) were believed 108,109 to arise from 96 in alkaline 2-methoxyethanol 108 or in the mixed solvent pentane/aqueous sodium hydroxide/phase transfer catalyst 109 via the dediazoniation of 97 with subsequent addition of halide 108 and other nucleophiles.…”

“…With regard to the rejected phenonium intermediate 363, an electrophilic π-attack of the carbenoid function at an sp 2 carbon atom appears to also be Cyclopropyl had appeared to migrate slower than phenyl but a little faster than methyl 107 in the putative carbenes generated from N-nitrosooxazolidones 96 in section 2.3.3, judging from competition with [1 + 2] cycloaddition; but the unknown demarcation line against the incipient alkenyl cation made this conclusion uncertain. A correspondingly modest migration rate of cyclopropyl in the carbenoid R-chloroβ,β-dicyclopropylvinyllithium 335 (373) in THF is indicated by the successful competition of bimolecular nucleophilic substitution: The alkyne 374 was produced between -90 °C and -60 °C; but the side products 376 (R ) n-Bu or t-Bu) arose slightly above -90 °C with the deprotonating agents RLi in excess.…”

Three-Membered-Ring-Based Molecular Architectures

“…418,419 An alternative synthesis of 565 started with the Reformatsky reaction of methyl 3-bromopropionate with dicyclopropylketone to furnish the dicyclopropylhydroxypropionic acid (604), and the latter was converted in four steps to 5,5-dicyclopropyl-3-nitrosooxazolidone (605), which, upon treatment with a base, gave 565 (Scheme 102). 420 Two other approaches started from cyclopropylmethyl cyclopropyl ketone 609 which was obtained from a reaction of cyclopropanecarbonyl chloride with 4-trimethylsilylbutene and subsequent cationic cyclization. The ketone 609 was either transformed into the gem-dichloride 606, which yields dicyclopropylethyne (565) by 2-fold dehydrohalogenation or by conversion to the selenadiazole 611 and its fragmentation upon treatment with n-butyllithium at low temperature (Scheme 102).…”

“…The first synthesis of dicyclopropylethyne ( 565 ) was accomplished by Köbrich et al applying a Fritsch−Buttenberg−Wiechell rearrangement of the carbenoid generated from 591 , which was obtained by a Wittig-type olefination of dicyclopropyl ketone ( 385 ) (Scheme ). , An alternative synthesis of 565 started with the Reformatsky reaction of methyl 3-bromopropionate with dicyclopropylketone to furnish the dicyclopropylhydroxypropionic acid ( 604 ), and the latter was converted in four steps to 5,5-dicyclopropyl-3-nitrosooxazolidone ( 605 ), which, upon treatment with a base, gave 565 (Scheme ) 102 …”