Dialkyl azodiformates form dihydrooxadiazines with indene, dihydro-1,4-dioxine, vinylene carbonate, cisand irons-1,2-dimethoxyethylene, and vinyl acetate by 1,4 addition; 1,2 addition yielding diazetidines is observed with vinyl ethers. Diazetidines also result from the addition of 4-phenyl-A'-1,2,4-triazoline-3,5-dione (PTD) to indene and dihydro-1,4-dioxine. Dihydrooxadiazines are formed in a concerted Diels-Alder reaction with inverse electron demand, the diazetidines via dipolar intermediates. The acceleration of azodiformate addition by illumination is due to the photochemical production of as azodiformates, which show increased thermal reaction rates compared with the irons isomers.

Twelve monoaryl enynic and diynic esters were synthesized and subjected to refluxing acetic anhydride. Seven underwent intramolecular Diels-Alder reactions. Propargyl phenylpropiolate (9) and phenylpropargyl propicíate cyclized to 3-hydroxymethyl-2-naphthoic acid lactone (lb), while irons-cinnamyl propiolate gave 3-hydroxymethyl-3,4-dihydro-2-naphthoic acid lactone. Derivatives of lb resulted from methoxy-and methylenedioxy-substituted compounds. Propargyl irans-cinnamate, allyl phenylpropiolate, and three derivatives of 9 did not cyclize. Purified samples of 9 and its derivatives exist as stable hydrates.Previous studies in our laboratory2-6 concerned the intramolecular Diels-Alder reaction of unsaturated dlaryl esters of the type Ar(C2)C02CH2(C2)Ar', where each (C2) unit is a -CH-CHor -Ce=Cgroup. For Ar and Ar' = phenyl or substituted phenyl groups, the products formed have the skeletal structures of 1or 4-phenyl-3-hydroxymethyI-2-naphthoic acid lactones (i.e., of cyclolignan lactones) la and 2a, respectively (where ring B may be in the dihydro or tetrahydro form). In the present work we investigated the syntheses and cyclizations of unsaturated monoaryl esters a, R = Ph; b, R = H of the types H(C2)C02CH2(C2)Ar' and Ar(C2)C02CH2-(C2)H. For Ar = Ar' = Ph intramolecular Diels-Alder reactions should lead to 3-hydroxymethyl-2naphthoic acid lactone (lb = 2b) and its hydro products.The esters prepared for cyclization and the cyclized products formed in our study are shown in Table I. Syntheses of the esters were effected by four different standard methods, as described in the Experimental Section. Ethyl 3,5-dimethoxyphenylpropiolate (18), needed to obtain 5 and 11, was prepared from 3,5-dimethoxybenzaldehyde and triethyl iodophosphonoacetate. Compound 18 could not be obtained through initial treatment of ethyl

A one-step synthesis of dihydrocyclolignan lactones (including r-apopicropodophyllin, 2c) from ¿rans-oinnamyl chlorides and sodium phenylpropiolates is described. Studies on polarographic and macroscale electroreductions of model a,¿3-unsaturated esters in the solvent-electrolyte acetonitrile-tetraethyl ammonium bromide are presented. In particular, electroreduction of 2c at controlled cathode potential gives rac-deoxypicropodophyllin (3) by trans addition of hydrogen to the conjugated carbon-carbon double bond.In previous papers2-4 we reported syntheses of cyclolignan lactones 2 by means of the intramolecular Diels-Alder reaction of irons-cinnamyl phenylpropiolates (1) in refluxing acetic anhydride. Formation of 1 from the corresponding phenylpropiolyl chloride and transcinnamyl alcohol, however, proved to be difficult or capricious in many cases.6 We now report an alternative synthetic procedure for 2 wherein the ester 1 is formed (from the corresponding (rans-cinnamyl chloride and sodium phenylpropiolate) in refluxing anhydrous dimethylformamide (DMF) and is cyclized in situ.6 Thus, cyclolignans 2a-c were obtained by this a

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bromides were quantitatively analyzed by integration on a Varían HA-60IL nmr spectrometer. Each integration was performed at least ten times. Reactions were run with varying quantities of bromine to ensure consistent results. Relative rate constants were calculated using the standard equation1 23 k/ko = In [(A, -X)/A"]/ln [( " -)/ "] where Ao and To are initial moles of hydrocarbon and toluene and X and Y are the corresponding moles of bromides obtained upon completion of the reaction. No reaction was carried beyond consumption of 30% of the methylarenes.