Cyclopropylphosphonium

Cyclopropylphosphonium salts are produced, together with the phosphonium salts (76), in reactions of ylides with vinylsulphonium salts... 

Vinylsulphonium salts and ylides gave cyclopropylphosphonium salts (95) via proton transfer in the initial adducts (94). C-Methylation of the ylides also occurred with dimethylvinylsulphonium salts, whereas the ylides (93 R = H, COPh, or /7-N08 CeHi) gave only the corresponding phosphonium salts. 

Among the real chemical species that have been developed along these lines are the cyclopropylphosphonium salts 1 and 2. 

Schweitzer s exploratory studies on the reaction of cyclopropylphosphonium bromide showed that this reagent is of a limited utility as an annelation reagent819,820. However,... 

More synthetic routes to the l-(hydroxymethyl)pyrrolizidines have been reported. Two groups3,4 have published the same route to ( )-isoretronecanol (3) (Scheme 1). The key step is the nucleophilic attack of succinimide anion on the cyclopropylphosphonium salt (1), followed by intramolecular Wittig reaction to generate the unsaturated pyrrolizidinone ester (2). Catalytic reduction and reduction with a hydride yielded ( )-isoretronecanol (3). Flitsch and Wernsmann achieved a higher overall yield (62%) by carrying out the first step in boiling xylene.3... 

This A -phosphane has been developed as a suitable building block in organic chemistry (see Section 5.13.1.). However, some higher homologues of the cyclopropylphosphonium salts have been synthesized. (3-Bromo-2-methylpropyl)triphenylphosphonium bromide was similarly converted into (2-methylcyclopropyl)phosphonium bromide upon reaction with sodium ethoxide in ethanol. ... 

The principal synthetic application of cyclopropylidenetriphenylphosphoranes 4 is the conversion with carbonyl compounds (aldehydes and ketones) into alkylidenecyclopropanes 5. As cyclopropyl halides do not react with phosphanes to form cyclopropylphosphonium halides vide supra), the generation of these precursors 3 is generally performed by condensation of 1,3-dibromopropanes 1 with triphenylphosphane and subsequent 1,3-dehydrobromination of the resulting salt 2 with one equivalent of base. A second equivalent of base generates the... 

Cyclopropylphosphonium salts are also equivalents of 1,3-diyls3,4. In this reaction the formal zwitterion is attacked by an electron-rich enolate. Typical applications are the reaction of cyclopropylphosphonium sails with ot-oxocycloalkanecarbaldehydes to give spirocyclic systems, however, yields are low and diastereoselcctivity is only moderate4. 

Partially hydrogenated pyrrolizines are easily obtained in high yield from a reaction of imides with cyclopropylphosphonium salt (195). Pyrrolizine ester (197) was obtained from succinimide, in a reaction via (196) phthalimide gave the benzopyrrolizinone (198) <80TL4585,81TL719>. Compound (199) was obtained from succinimide with triphenylcyclopropylphosphonium tetrafluoroborate... 

Facile cycloalkenylations of carbonyl groups have been carried out with cyclopropylphosphonium fluoroborates . Complex carbocyclic systems, such as the sesquiterpene a-cedrene, can be effectively constructed by cationic cyclization Epoxide cleavage which follows upon dissolving metal reduction of proximal cyclopropane rings makes possible the ready synthesis of functionalized strained ring compounds inaccessible by other methods... 

A full report has been published on the annulation of the -keto-ester (83) by the cyclopropylphosphonium salt (84) leading to (85) hydrolysis of the intermediate vinyl sulphide was effected by an iodolactonization procedure, as standard methods failed. An alternative annulation method (Scheme 8) involves the acylation of vinyl cuprates by unsaturated acid chlorides followed by Nazarov cyclization MeaSil can sometimes serve as a good reagent for this step. Nazarov-type cyclizations using acetylenic acetals have also been employed in... 

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