Acetylenic esters rearrangement

Sometimes the acetylenic ester rearranges to the corresponding allenic ester. For example, when the triethylamine salt of 3-chloro-2-ethoxycarbonyl-4-phenyl-2-hexenoic acid is refluxed in toluene, the allenic ester and acetylenic ester are obtained in a ratio of 3 7 (total yield 70%). There are alternative routes to cyclopropylpropiolic acids and esters, such as adding butyllithium to corresponding acetylenes and treating the product with carbon dioxide or methyl chloroformate. ... 

The 7-azaquadricyclane (77), like its precursor (12), shows evidence in the NMR spectrum of restricted rotation about the N-CO bond. All the 7-heteroquadricyclanes, 76-79, are thermolabile, and they rearrange very readily to the corresponding azepines (80) or oxepin (81). (In another instance the 7-oxabicyclo[4.1.0] valence-bond tautomer was obtained instead. ) In appropriate conditions the addition of acetylenic esters (methyl propiolate and dimethyl acetylene-dicarboxylate) competes successfully with the isomerization and gives the ca o-tricyclic adducts 82 or 83. " °... 

Anomalous cycloaddition reactions from benzocinnoline A-alkyli-mides and acetylenic esters were also described, in 1974, by Rees et al. 59 Benzocinnoline Af-alkylimides (487 and 488) gave adducts 492 via the sequence shown in Scheme 10 with acid, they rearranged to the imidazoles 493 and 494. 

Various functionalized alkynes can be submitted to carbocupration reactions, such as alkoxyalkynes,150 alkynyl carbamates,151 acetylenic orthoesters,152 and thioalkynes.153 The carbocupration of orthoesters, for example, 204, has been used to prepare a-substituted esters of the type 206 by acidic hydrolysis of the adduct 205 (Scheme 51).152 This allows the formation of regioisomers that are not accessible by copper-mediated addition to acetylenic esters. A stereoselective synthesis of trisubstituted alkenes has been described by Normant et al.lSd> starting from phenylthio-acetylene 207. Carbocupration with lithium di- -butylcuprate affords the intermediate 208 which, upon addition of /z-butyllithium, undergoes a 1,2-metalate rearrangement to the vinylcuprate 209. The latter can be trapped with various electrophiles, for example, ethyl propiolate, providing product 210 with complete regio- and stereocontrol. 

FRIEDLANDER Quinoline synthesis t32 FRIES Phenol ester rearrangement 133 FRITSCH. BUTTENBERG - WIECHELL Acetylene synthesis 134... 

This synthesis has been adapted to make the natural (5 -isomer of 114, reducing the initially formed aldehyde to (S)-114 with baker s yeast. [This same synthesis has been adapted to make (S)-callosobruchic acid (115), see below]. Julia s synthesis of a-geraniol (73) was also extended to make 114 by hydro-boration. Hydroboration of 73 with diisopinocampheylborane (made from (- )-a-pinene [(-)-116]) gave only a small ee however. A synthesis of ( )-114 started with the reaction of 2-methylpropiolactone and the ethylene acetal of 3-oxobutylmagnesium bromide. The methyl ester of the acid 117 thus prepared was chain-lengthened by reaction with acetylene and rearrangement with a vanadium catalyst of the ynol thereby obtained. The aldehyde 118 was then reduced with lithium aluminum hydride to 114. ... 

Isothiazoles are reported to yield the lactam (101) on reaction with diphenyl ketene <85BSB149>. Ethyne dicarboxylate esters add to 2,1-benzisothiazole to generate quinoline esters (102), and benzyne reacts to yield aeridine <83H(20)489, 88JCS(Pl)2l4l>. 2-Methyl-2,l-benzisothiazolin-3-thione with acetylene esters forms 2-iminobenzoquinone methides (103), which dimerize to give diazocines (104) or further react with the ethyne ester to yield diadducts (105). The initial adduct formed with phenylethyne and 2-methyl-2,l-benzisothiazolin-3-thione rearranges to produce l,2-dithiole[3,26]... 

In tetrahydrofuran the dihydrofurans 8 (X = O, n = 1) react with maleic anhydride at room temperature to yield pyrano[4,3-c]pyridines 205 via a complex addition-rearrangement scheme123 involving betaine 206 (Scheme 51). Furthermore, in the formation of the naphthyridines 207 and 208 from 13 and acetylenic esters or methyl acrylate, the first step consists of a Michael-type attack on the electron-rich C-3116 (Scheme 52). 

Addition of acetylenic esters to cyclic enamines leading by rearrangement ring expansion to cyclic ketones with two more carbon atoms. 

The homochiral acetylenic alcohol 2 [derived from ( )-4-benzyloxy-2-butenol by asymmetric Sharpless epoxidation via 2 in four steps] is transformed either to ( )-3 by treatment w ith lithium aluminum hydride or to (Z)-4 by hydrogenation with Lindlar catalyst. Simple Claisen or ortho ester rearrangement yield the same, but enantiomeric, products 5 and 6 with 85-90% ee288. 

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