Acid-promoted rearrangement

STEREOCONTROLLED PREPARATION OF 3-ACYLTETRAHYDROFURANS FROM ACID-PROMOTED REARRANGEMENTS OF ALLYLIC KETALS (2S,3S)-3-ACETYL-8-CARBOETHOXY-2,3-DIMETHYL-1-OXA-8-AZASPIRO[4.5]DECANE... [Pg.271]

Acid-promoted rearrangement of 4,4-disubstituted cyclohexadienones to 3,4-disubstituted phenols. [Pg.202]

Bicyclic systems 146 have been further elaborated into other natural productlike structures by acid-promoted rearrangement, which affords fused tricyclic systems [125], or by ring-opening/ring-closing metathesis processes [123, 126], after installing allyl groups into the structure. [Pg.25]

Ilyin A, Kysil V, Krasavin M, Kurashvili I, Ivachtchenko AV (2006) Complexity-enhancing acid-promoted rearrangement of tricyclic products of tandem Ugi 4CC/intramolecular Diels-Alder reaction. J Org Chem 71 9544—9547... [Pg.39]

While many functional groups are accommodated by this process, acid-promoted rearrangements and eliminations are not uncommon (equations 228-231).336-360 In fact, the hydration of certain unsaturated alkynes produces oxygen heterocycles (equations 232 and 233).361,362... [Pg.304]

Details of the regioselective preparation of a variety of new 2,4-disubstituted oxazoles, using both iodide- and acid-promoted rearrangements of TV-acylaziridines, have been presented.584 It has been shown585 that two plausible mechanisms (S i and/or two 5n2 reactions) can account for the acid-catalysed transformation of 1-acylaziridines (447) to oxazolines (448), while the regioselective rearrangement of... [Pg.582]

The oxirane fused azepine 40, formed by an intramolecular [5+2] cycloaddition reaction undergoes an acid promoted rearrangement to yield the tricyclic derivative 41. The structure was confirmed by X-ray crystallography of the nitrobenzoate ester <07OL4681>. [Pg.436]

Hopkins, M. H., Overman, L. E., Rishton, G. M. Stereocontrolled preparation of tetrahydrofurans from acid-promoted rearrangements of... [Pg.658]

Stereocontrolled Preparation of 3-Acyltetrahydrofurans from Acid-Promoted Rearrangements of Allylic Ketals (2S,3S)-3-Acetyl-8-carboethoxy-2,3-dimethyl-1-oxa-8-azaspiro-[4.5]decane. [Pg.281]

One of the most general approaches to the synthesis of this type of compounds involves the Lewis acid promoted rearrangement of acetals of a-substituted propiophenones [4,5]. Besides silver salts, a large variety of soft and borderline Lewis acids have been found to be convenient catalysts for the 1,2-aryl shift, noticeably zinc halides in substoichiometric amounts [6]. As final products need to be free of metal traces for human consume, the use of Lewis acids supported on microporous solids can be advantageous since a better recovering of the catalyst can be anticipated. [Pg.654]

Derivative 441 is an extremely useful intermediate for the construction of highly functionalized chiral tetrahydrofiirans via Lewis acid-promoted rearrangement of allylic acetals. This is elegantly demonstrated by the synthesis of optically pure (-h )-muscarine tosylate (446) [138] (Scheme 62). [Pg.60]

The acid-promoted rearrangement of the diazo-compound (130), prepared by the reaction of ethyl lithiodiazoacetate with isochroman-4-one, gave the new 2-benzoxepin system (131) a similar sequence, starting with chroman-4-one, gave the analogous 1-benzoxepin. Both were de-ethoxycarbonylated by a mild... [Pg.347]

In addition to (3-elimination, epoxides are also known to undergo rearrangement to a carbonyl group, and this reactivity can be synthetically useful as well. For example, Kita and co-workers <97JOC4991> have used a novel acid-promoted rearrangement of cyclic a,(3-epoxy acylates e.g., 110) for the stereoselective synthesis of spirocyclanes (e.g.. Ill), a technique which is... [Pg.60]

Also known as benzidine rearrangement or semidine rearrangement. Acid-promoted rearrangement of hydrazobenzene to 4,4-diaminobiphenyl (benzidine) and 2,4-diaminobiphenyl. [Pg.659]

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