Ring opening with methoxide

The initial products of organocatalytic epoxidation and aziridination can be ring opened with methoxide. In this way, tra/zs-dihydrorgrlation and frans-aminohydrorq lation of a,p-unsaturated aldehydes was achieved (Scheme 8.44). ... 

Using the general method described in Section 7.08.10.2 <74JHC163> 3-(phenylsulfonyloxy) pyrido[4,3-fi ]pyrimidine-2,4-dione (590) ring opens with sodium methoxide and rearranges to a hydrazinopyridine ester, which in refluxing acid yields l//-pyrazolo[4,3-c]pyridin-3-one (591) (Equation (59)). 

When methyl 2-(trimethylsiloxy)cyclopropanecarboxylates 17 were treated with potassium borohydride in methanol, y-butyrolactones 18 were obtained in high yield. The first step in this reaction is thought to be desilylation and ring opening by methoxide ion generated in situ from methanol and borohydride. Subsequent reduction of the ketone leads to the secondary alcohol that reacts intramolecularly with the ester group to give the lactone. 

Substituted furan-3(2//)-ones, generated by Claisen-rearrangement from 3-allyloxy furanes can also serve as versatile substrates in photocycloaddition chemistry, as described by P. Margaretha. The cycloadducts, which are formed with high regioselectivity, can be ring-opened with sodium methoxide to afford diastereomerically pure bicyclo[3.2.0]hep-tane derivatives. 

The triazine (239) undergoes ring-opening with sodium methoxide in methanol as well as giving the triazine (240). The action of sodium ethoxide gives the open-chain ethyl analogue and the triazine (238). ... 

Y = F) with sodiiun methoxide, but undergoes ring-opening with potassium hydroxide in t-butyl alcohol to give the acid o-C F4H-CF CF-C02H, whidi is converted into the dichloro-compound o-CsFaH-CFCl-CFCl-COaH by treatmmt with phosphorus pentachloride followed by hydrolysis. Both 3-chloroh tafluoro-and octafluoro-indene are converted into the oxo-sulphonic add (32) by 20% oleum, and the dibromide (33a) or the nitro-indane (33b) is formed when octa-fluoioindene reacts with bromine or HNOa-HF, respectively. The fomiation of the antiaromatic cabocation (34) when octafluoroindene dissolves in SbFs-SOa at -40°C has been briefly studied by n.m.r. spectroscopy. ... 

The oxaziridine ring itself is stable towards alkali there is, for instance, no substitutive ring opening by hydroxyl ions as in oxiranes. 2-r-Butyl-3-phenyloxaziridine (56) is not attacked by methoxide ion in methanol during 12 h at room temperature 3-isopropyl-2-r-octyloxaziridine does not react at room temperature with either solid potassium hydroxide or potassium methoxide solution (57JA5739). 

With strong nucleophiles such as methoxide, ring opening follows an Sn2 mechanism. Examine the next to lowest-unoccupied molecular orbital (LUMO+1) for propylene oxide. On which carbon is it most heavily concentrated Is this also the least crowded carbon (Examine a spacefilling model for propylene oxide.) What should be the product of Sn2 addition ... 

Starting from l.l-dichloro-7b-ethoxy-2-methyl-1,1 a,2,7-tetrahydrobenzo[/)]cyclopropa[prepared from the corresponding benzothiopyran by addition of dichlorocarbene, the three 1-benzothiepins 6a-c are formed upon treatment with strong bases, i.e. sodium methoxide or ethoxide in dimethyl sulfoxide.73 The optimal yield of each 1-benzo-thiepin compound depends on the molar equivalents of base, as follows from different ring-opening mechanisms. 

Azabicyclo[4.1.0]hept-3-enes, e. g. 13, are available from 1,4-dihydrobenzenes 12 by the route indicated, and are useful precursors for the synthesis of specifically substituted 1//-azepines free from isomeric contamination.61 For example, low temperature addition of bromine to bicycle 13 yields the dibromo derivative 14 which, with powdered sodium methoxide in tet-rahydrofuran, undergoes a double dehydrobromination followed by electrocyclic ring opening of the resulting 7-azabicyclo[4.1.0]hepta-2,4-diene 15 to give methyl l//-azepine-l-carboxylate (16). 

The cycloadduct, l-phenyl-2,3-dihydro-l-benzothiophenium salt 59 is quite stable in the presence of hydroxide or methoxide anions at room temperature. When cycloadduct 59 reacted with sodium methoxide in methanol at 50 °C for 12 h, the ring opened product 243 was obtained in 96% yield (Scheme 41) <2003JOC731>. 

The reactivity of these tricyclic compounds has been investigated in detail. Reaction of these with sodium cyanoborohydride in acetic acid reduces the imine double bonds to give the tetrahydro-derivatives, for example, 37 gives 39. Reaction of 37 with sodium methoxide results in the ring-opened sulfonate salt 40 re-acidification of this salt gives the corresponding sulfonic acid which cyclizes back to the tricycle 37. Further heating of the sulfonic acid... 

A ring opening reaction of (1-lactams promoted by methoxide generated nitrogen nucleophiles in situ that subsequently added to proximal allenes producing trisubstituted pyrroles <06CC2616>. In the event, treatment of (3-lactam 3 with MeONa led to pyrrole-2-acetic ester 4 after cleavage of the amide bond, 5-exo-dig cyclization, and loss of methanol. The sequence was notable as no metal catalyst was required. 

The vinyl silane 247 was unmasked to the ketone 250 by epoxidation, subsequent ring opening of the epoxide with HF in pyridine and concurrent cleavage of the THP and TBS protecting group (Scheme 39). The Stork-Jung annulation was completed through the treatment of the diketone 250 with sodium methoxide to mediate the intramolecular aldol con-... 

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