Carbanion rearrangements. Collison induced dissociations of deprotonated alkyl acetoacetates
摘要:
AbstractDeprotonation of methyl acetoacetate yields two enolate ions MeCOC̄HCO2Me (a) and C̄H2COCH2CO2Me (b). On collisional activation, ions a and b fragment differently. The major fragmentation of a is specific loss of MeOH through a four‐centred transition state to form −O(Me)CCCO. In contrast, ion b eliminates CH2CO to give −CH2CO2Me. Some rearrangement of b to a is also noted. Rearrangement of a to b is very minor under single collision conditions but at high collision gas pressure rearrangement of a to b is strongly promoted. Similar effects are observed in the collisional activation spectra of MeCOC̄(Me)CO2Me (c) and −CH2COC(Me)CO2Me (d). The loss of MeOH from (c) proceeds via a six membered transition state to −CH2COC(Me)CO; this is a stepwise process in which the deprotonation (step two) is not rate determining. A number of other decompositions occur, these have also been studied by deuterium labelling.
M(NO 3)2 · X H 2 O,TNCB,TBAP和HMTAI对1,4-二氢吡啶进行快速有效的芳构化,并由硝苯地平d 3制备氘标记的脱氢硝苯地平
摘要:
在100°C的乙酸中,使用各种金属硝酸盐,溴化三硝酸铈(IV)溴酸盐(TNCB)和高碘酸四丁铵(TBAP)作为氧化剂,研究了各种1,4-二氢吡啶的简便有效芳构化。碘(HMTAI)在甲醇中回流。nifedipine-的有效转化d 3至dehydronifedipine- d 3作为内标可以以硝苯地平浓度的在体内测定中使用。