Cyclopropanecarboxylate ester alkene

Cyclopropanation. Platinum(lV) chloride is able to induce the formation of cyclopropanecarboxylic esters from alkenes and diazoacetic esters at 80° (10 examples, 70-95%). 

Formation of cyclopropanecarboxylic esters by capture of the metal-carbenoid derived from diazoacetates with alkenes is rendered enantioselective by a chiral 2,2 -bipyridine (2) [complexed to Cu] and a bis(oxazolinyl)pyridine (2a) [complexed to Ru]. ... 

Cyclopropanecarboxylic esters are conveniently available, even from volatile alkenes, because CuOTf promotes cyclopropanations in good yields at low temperatures. Thus trans- and cis-2-butenes, boiling under reflux, react stereospecifically with ethyl diazoacetate to produce the corresponding ethyl 2,3-dimethyl-cyclopropanecarboxylates (eq 3 and eq 4), and cyclobutene reacts with ethyl diazoacetate at 0 °C to deliver a mixture of exo-and e/i[Pg.159]

Cyclopropanecarboxylic esters have been prepared, in 75—86 % yield, by intramolecular alkylation of 4-chloroalkyl esters, using phase-transfer catalysis. Monoalkylation of nitro-alkenes by acrylic esters occurs in a controlled manner if a two-phase system is used, to give products of Michael addition in 45—65 % yield for five examples. An interesting variant on this reaction involves the generation of the a-nitro-carbanion by conjugate reduction of a nitroalkene with sodium borohydride followed by its conjugate addition to methyl acrylate yields of 62—95% are reported for five cases (Scheme 39). ... 

The cyclopropanation of gaseous alkenes, butadiene, and allene (see Section 1.2.1.2.4.2.6.3.3., Table 11, entry 1) by diazoacetic esters can be achieved by passing a vapor-gas mixture of the alkene and the diazo compound at atmospheric pressure through a tubular continuous flow reactor which contains a copper catalyst (ca. 10%) deposited on pumice. In this manner, alkyl cyclopropanecarboxylates were obtained in yields of up to 50% with cop-per(II) sulfate (typical reaction temperature 65-110"C, contact time 3.6 s) or copper(II) oxide (85-200°C, 5s) as catalysts. 

There are few examples of the reactions of alkenes with diazoesters of chiral alcohols which give high face discrimination in rhodium-catalyzed reactions [936, 1497). However, Davies and coworkers [192, 193, 1503] have performed the reactions of alkenes with vinyldiazoesters of chiral alcohols under Rh2(OAc)4 or better yet Rh2(OCOC7H j 5)4 catalysis. The ester of (K)-pantolactone 1.16 is the most efficient substrate, and ftum-cyclopropanecarboxylates are obtained highly selectively. Starting from 7.141 (R = Ph), the enantioenriched plant hormone l-amino-2-phenylcyclopropanecarboxylic acid has been prepared (Figure 7.88). 

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