[reaction: see text] Tetramethylpiperidinyloxy (TEMPO, TO*) reacts with a variety of ketenes R1R2C=C=O by rate-limiting attack on carbonyl carbon to give the 1,2-bis(adducts) R1R2C(OT)CO2T. The alpha,beta-unsaturated ketenes (E)-PhCH=CHCH=C=O (8b) and PhC=CCH=C=O (8c) give the 1,4-bis(adducts) PhCH(OT)CH=CHCO2T and PhC(OT)=C=CHCO2T. The ketenes may be generated in situ for these reactions in the presence
                                    [反应:参见文本]四甲基
哌啶基氧基(
TEMPO,TO *)通过限制对羰基碳的进攻,与各种烯酮R1R2C = C = O反应,得到1,2-双(加合物)R1R2C(OT)CO2T。α,β-不饱和烯酮(E)-PhCH = CHCH = C = O(8b)和PhC = CCH = C = O(8c)得到1,4-双(加合物)PhCH(OT)CH = CHCO2T和PhC(OT)= C = CHCO2T。对于这些反应,在
TEMPO存在下,可通过R1R2CHCOCl的Et3N脱
氯化氢或Wolff重排原位生成烯酮。Ketenes PhCH = C = O(8a),8b和8c以前在室温下未发现为长寿命物种,但是当通过光
化学Wolff重排形成时,可以通过常规IR光谱法在溶液中表征并用于动力学使用紫外线检测研究与
TEMPO的反应。