Teacher:In this task, you will be given a passage to read. A fill in the blank question will be given to you.  Your answer should fit the blank appropriately.
Teacher: Now, understand the problem? Solve this instance:  Catalytic reagents have been less successful , with most variations suffering from poor yield , poor enantioselectivity , or both . There are also issues with substrate scope , most having limitations with methylene transfer and aliphatic aldehydes . The trouble stems from the need for a nucleophilic sulfide that efficiently generates the ylide which can also act as a good leaving group to form the epoxide . Since the factors underlying these desiderata are at odds , tuning of the catalyst properties has proven difficult . Shown below are several of the most successful catalysts along with the yields and enantiomeric excess for their use in synthesis of ( E ) -stilbene oxide . Aggarwal has developed an alternative method employing the same sulfide as above and a novel alkylation involving a rhodium carbenoid formed in situ . The method too has limited substrate scope , failing for any electrophiles possessing basic substituents due to competitive consumption of the carbenoid . Treaty of Ciudad Juárez  The Treaty of Ciudad Juárez was a peace treaty signed between the then President of Mexico , Porfirio Díaz , and the revolutionary Francisco Madero on May 21 , 1911 . The treaty put an end to the fighting between forces supporting Madero and those of Díaz and thus concluded the initial phase of the Mexican Revolution . The treaty stipulated that Díaz , as well as his vice president Ramón Corral , were to step down by the end of May , and that he was to be replaced by Francisco León de la Barra as interim president and hold presidential elections . Those who had suffered losses due to the revolution would be the indemnified , and there would be a general amnesty . Díaz resigned on May 25 , and interim president Francisco León de la Barra was the new incumbent . Díaz and his family , his vice president Corral , plus José Yves Limantour and Rosendo Pineda left Mexico for exile . Significantly , the treaty did not mention or institute any social reforms that Madero had vaguely promised on previous occasions . It also left the Porfirian state essentially intact . Additionally , Madero supported the unpopular idea that all land disputes were to be settled through the courts , staffed by the old judges , a decision that led to outbreaks of sporadic violence , particularly in rural areas . On June 7 , 1911 , Madero entered Mexico City . In October 1911 he was elected president , under the banner of the Partido Constitucional Progresista , along with José María Pino Suárez , his new running mate as vice @-@ president . Madero pushed aside Francisco Vázquez Gómez , the vice presidential candidate for the Anti @-@ Reelectionist Party in 1910 , as being too moderate . fill in the blank  :  Catalytic reagents have been less successful , with most variations suffering from poor __________________ , poor enantioselectivity , or both . 
Student:
 yield 