Ethers propargylic, reaction with

Reaction with Propargyl Halides. The indium-mediated coupling of propargyl bromide with a variety of imines and imine oxides afforded homo-propargylamine derivatives in aqueous media under mild conditions.78 Propargylation of glyoxylic oxime ether in the presence of a catalytic amount of palladium(O) complex and indium(I) iodide in aqueous media was also studied (Eq.11.47).79... 

Also studied was the effect of ether, which behaves as a retarder, on the polymerization. The retardation is most marked with the di- and trihalides and least with the monohalide and Zr (allyl) 4. In fact if large amounts of ether are present from the preparation, Zr(allyl)2Br2 shows hardly any activity at all. To avoid any possibility of contamination by ether, the halides in Table XI were prepared from pure ether-free Zr(allyl)4 in toluene by reaction with propargyl bromide. 

However, the classical version of the ABAC, when triallyl-, trimethallyl-, or tricrotylborane are involved in the reaction with RR1CHC=CH (e.g., propargylic ethers), can be applied only for the synthesis of 1-boraadamantane derivatives 35, 3,5-dimethyl- 36 and 4,6-dimethyl-l-boraadamantanes 37 (Scheme 7). Hence, the stmctures of the final cage compounds are rigidly restricted by the stmctures of the starting allylic boranes. 

Vinylidenecarbene or allenylidene3 (R)2C=C=C has a lance-shaped, unsubstituted and sp-hybridized carbene center and, therefore, will not be easily subject to steric hindrance in its insertion reactions. On this assumption, (2-methyljpropenylidenecarbene or its carbenoid was chosen as a prototype of typical vinylidenecarbenes and its insertion reaction with several different types of alkoxides was investigated by employing two methods (A and B, Scheme 10) for carbene generation.20 The insertion products 20 were obtained almost exclusively except lithium allyloxide (Table 4, entry 10).21 By-products such as propargyl ether and allenyl ether were not formed at all. To be noted here, in... 

If the addition involves an alkynyllithium such as 34, the first-formed alkoxide intermediate 35 isomerizes into the propargylic-allenic lithium reagent. Reactions with electrophiles lead to either 36a or the allenol silyl ethers 36b (equation 13). ... 

Norpseudoephedrine-derived amino ether 81 was also used as a chiral coordinating agent for the enantioselective [2,3]-Wittig rearrangement. The rearrangement of propargyl ether 82 induced by n-BuLi/81 provided allenyl alcohol (5 )-83 in 62% ee (equation 45). In contrast, a similar reaction with (-)-24 provided only 9% ee of (S)-S3. 

Plumet et al. described domino metathesis of propargyl (2-endo-7-oxanorborn-5-enyl) ethers 62a-62c with allyl acetate in the presence of Grubbs ruthenium catalyst Ic (Scheme 22). The reaction proceeds stereoselectively to produce substituted m-fused bicyclic ethers 63a-63c. In a similar manner, indolizidinone derivative 64 is obtained from compound 62d instead of pyrrolizidine derivative 63d. ... 

Iodobenzyl propargyl ether 57 cyclizes with 7t-allylpalladium (Scheme 18) to form after trapping by a secondary amine tetrahydro-2-benzoxepines 58 in 70% yield. The piperidino derivative 58 (R2 = (CH2)5) undergoes Diels-Alder reaction with 4-phenyl-l,2,4-triazole-3,5-dione as dienophile to give a spiro derivative 59 in 44% yield <1996TL6565>. 

The resulting propargylic alcohol is protected as TIPS ether by a standard procedure using the corresponding silyl chloride and imidazole in DMF. Optionally the more reactive silyl triflate and 2,6-lutidine may be employed in order to shorten the reaction time. Under acidic conditions TIPS and TPS are nearly stable protecting groups. Therefore the TBS ether is selectively cleaved with acetic acid even in presence of the acetal moiety.13 Subsequent reaction with iodine and triphenylphosphine, known as the Appel reaction14, provides the desired iodide 4. 

The use of Rh2(5/ -MEPY)4 and Rh2(55-MEPY)4 for reactions with menthyl diazoacetates (MDA) also produces an enormous double diastereoselection not previously observed to the same degree in cyclopropanation reactions. With methyl propargyl ether, for example, Rh2(5/ -MEPY)4 catalyzed reactions of d-MDA yield 16 (R = CH3OCH2) in 98% diastereomeric excess (de), but /-MDA produces its diastereoisomer in only 40% de with Rh2(55-MEPY)4, /-MDA gives the higher de (98%) and d-MDA gives the lower de (43%). Similar results are obtained from reactions of MDA with 1-hexyne and 3,3-dimethyl-1-propyne. The diazocarboxylate substituent obviously plays a critical role in establishing the more effective carbene orientation for addition to the alkyne. 

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