Ethyl 2-cyclopropylideneacetate

The reactivity of ethyl cyclopropylideneacetate (52b) has been exploited by Spitzner and Sawitzki in a new (formal) total synthesis of the diterpene ( + )-isoeremolactone 80 (Scheme 16) [25]. The key step of the synthesis is the addition of the enantiomerically pure dienolate 78 to the reactive acrylate 52b, to give a single isomer 79 in 92% yield. 

Cycloaddition of the nitrone (595a) with ethyl cyclopropylideneacetate (596) gave diastereomeric adducts (597) and (598) in good yield. They were obtained in a 5 1 ratio via anti-endo and anti-exo approaches (Scheme 2.266) (777). 

PPE-induced cyclization was also employed in the synthesis of a spirofused YCK analogue (103) (Scheme 7) (64). The precursor spiro acid 102 was obtained from the Diels-Alder reaction between the diene (101) and ethyl cyclopropylideneacetate. Diels-Alder reaction of diene 97 with maleic anhydride afforded adduct 104, which on... 

Alkylidenecyclopropanes have shown an interesting reactivity, which was exploited to develop several metal-catalyzed cycloadditions [13], Among them, the nickel-catalyzed [4+3] cycloadditions between ethyl cyclopropylideneacetate and 1,3-dienes is an efficient synthetic procedure for the preparation of cycloheptenes (Scheme 8.4) [14]. Up to 70% cycloheptene has been obtained with a catalytic system combining Ni(cod)2 and tri-o-biphenylyl phosphite. A key parameter of the reaction is the slow addition of both substrates otherwise, yields dramatically dropped. In the case of dissymmetric 1,3-dienes, the cycloaddition did not show any selectivity except for isoprene (R = H, = Me, Scheme 8.4), where the ii-isomer is predominately obtained (5 1 ratio). 

In the presence ofnickel(O) catalysts, ethyl cyclopropylideneacetate participated in [3+2+2], [4+3], and [4+3+2] annulation to furnish medium-sized carbocy-cles (Table 2.5) [116]. Synthesis of seven-membered ring compounds by formal o-bond metathesis between the MCP and four-membered ring compounds was also achieved [117]. 

Other esters of 2-chloro-2-cyclopropylideneacetic acid can easily be prepared from the methyl esters 1-Me, 2-Me by transesterification with the appropriate alcohol component under titanium tetraisopropoxide catalysis [20], as has been demonstrated for a number of benzyl and ethyl esters (Scheme 4) [9,10,21,22a]. 

Michael addition of primary selenoamides to ethyl 2-bromo-2-cyclopropylideneacetate and then intramolecular substitution gave 5-spirocyclopropane-annulated 4,5-dihydro-l,3-selenazole-4-carboxylates 77 (Equation 19) <2004SL329>. 

This type of sequence, namely reaction of ethyl 2-cyclopropylideneacetate with lithium 9-tert-butoxy-l-methylbicyclo[4.3.0]nona-3,5-dien-4-olate (28) to give cycloadduct 29, has been utilized in the enantioselective synthesis of (- -)-isoeremolactone. ... 

Spirocyclopropane-annulated selenaoline-4-carboxylates 293 are synthesized in good yields via Michael addition of selenoamide 291 to ethyl 2-bromo-2-cyclopropylideneacetate 290 followed by an intramolecular substitution imder basic conditions <04SL329>. 

Scheme 21 Asymmetric [3+2] cycloaddition of azomethine ylides with ethyl 2-cyclopropylideneacetate [39]...

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