CN103429082B - 4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法 - Google Patents

4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法 Download PDF

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CN103429082B
CN103429082B CN201280014379.0A CN201280014379A CN103429082B CN 103429082 B CN103429082 B CN 103429082B CN 201280014379 A CN201280014379 A CN 201280014379A CN 103429082 B CN103429082 B CN 103429082B
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pyridine
formonitrile hcn
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朱远明
G.T.怀特克
K.E.阿恩特
J.M.伦加
R.D.弗洛斯
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Corteva Agriscience LLC
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Abstract

4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯是通过一系列步骤方便地从3,4,5,6-四氯吡啶-2-甲腈制备的,所述步骤包括氟交换、胺化、与肼反应、卤化、水解和酯化及过渡金属辅助的偶联。

Description

4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法
技术领域
本发明涉及4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法。更具体而言,本发明涉及其中5-氟取代基是在操作方案早期通过卤素交换引入的4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法。
背景技术
美国专利6,297,197B1特别地描述了某些4-氨基-3-氯-5-氟-6-(烷氧基或芳基氧基)吡啶-2-甲酸酯化合物及其作为除草剂的用途。美国专利6,784,137B2和7,314,849B2特别地描述了某些4-氨基-3-氯-5-氟-6-(芳基)吡啶-2-甲酸酯化合物及其作为除草剂的用途。美国专利7,432,227B2特别地描述了某些4-氨基-3-氯-5-氟-6-(烷基)吡啶-2-甲酸酯化合物及其作为除草剂的用途。这些专利中每个都描述了通过相应的5-未取代的吡啶-2-甲酸酯与1-(氯甲基)-4-氟-1,4-二氮鎓二环[2.2.2]辛烷二(四氟硼酸盐)的氟化来制造4-氨基-3-氯-5-氟吡啶-2-甲酸酯起始物质。不必依赖于用昂贵的氟化剂如1-(氯甲基)-4-氟-1,4-二氮鎓二环[2.2.2]辛烷二(四氟硼酸盐)对吡啶-2-甲酸酯的5-位进行直接氟化对于生成4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯而言将会是有利的。
发明内容
本发明涉及从3,4,5,6-四氯吡啶-2-甲腈制备4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的方法。更具体而言,本发明涉及式I的4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法
其中
R表示C1-C4烷基、环丙基、C2-C4烯基或苯基,所述苯基被1至4个取代基所取代,所述取代基独立地选自卤素、C1-C4烷基、卤代C1-C4烷基、C1-C4烷氧基或卤代C1-C4烷氧基;和
R1表示C1-C12烷基或者未取代的或者取代的C7-C11芳基烷基;
其包括下列步骤:
a)用氟离子源氟化3,4,5,6-四氯吡啶-2-甲腈(式A)
以生成3-氯-4,5,6-三氟吡啶-2-甲腈(式B)
b)用氨胺化3-氯-4,5,6-三氟吡啶-2-甲腈(式B)以生成4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(式C)
c)使得4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(式C)6-位的氟取代基与肼反应以生成4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(式D)
d)用氯、溴或碘源卤化4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(式D)以生成式E的4-氨基-3-氯-5-氟-6-卤代-吡啶-2-甲腈
其中L是Br、Cl或I;
e)用强酸和醇(R1OH)水解并酯化式E的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲腈以生成式F的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲酸酯
其中L和R1,如先前所定义;和
f)将式F的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲酸酯与式G的芳基金属化合物、烷基金属化合物或烯基金属化合物在过渡金属催化剂存在下偶联以生成式I的4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯,所述式G为:
R-Met         G
其中R如先前所定义且Met表示Zn-卤化物、Zn-R、三-(C1-C4烷基)锡、铜或B(OR2)(OR3),其中R2和R3彼此独立地是氢、C1-C4烷基或一起形成亚乙基或亚丙基。
如方案I中所描述,a)到f)的步骤可以以所列次序进行,或者可将某些步骤重排成为化学相容性所允许的不同次序。例如,步骤f)的偶联可以先于步骤e)的水解和酯化进行。
方案I
本发明的另外方面涉及增加可回收的3-氯-4,5,6-三氟吡啶-2-甲腈(式B)的量的改进方法
所述化合物是用氟离子源通过氟化3,4,5,6-四氯吡啶-2-甲腈(式A)制备的
其中所述改进包括以下步骤:
i)分离来自氟化3,4,5,6-四氯吡啶-2-甲腈的过度氟化的3,4,5,6-四氟吡啶-2-甲腈(H)副产物
ii)使得分离出的3,4,5,6-四氟吡啶-2-甲腈(H)(a)与氯化锂(LiCl)反应,(b)在相转移催化剂存在下与3,4,5,6-四氯吡啶-2-甲腈(式A)反应或者(c)与LiCl和3,4,5,6-四氯吡啶-2-甲腈的组合反应以生成主要由3,4,5,6-四氯吡啶-2-甲腈、一氟-三氯吡啶-2-甲腈和二氟-二氯吡啶-2-甲腈组成的混合物;和
iii)将主要由3,4,5,6-四氯吡啶-2-甲腈、一氟-三氯吡啶-2-甲腈和二氟-二氯吡啶-2-甲腈组成的混合物重复利用到制备3-氯-4,5,6-三氟吡啶-2-甲腈(式B)的氟化反应中。
本发明的另一个方面是本方法过程中生成的新型中间体,即,以下化合物:
具体实施方式
如本申请所用,术语“烷基”、“烯基”和“炔基”以及衍生术语例如“烷氧基”、“酰基”、“烷基硫基”和“烷基磺酰基”,在其范围之内包括直链、支链和环状部分。除非另有具体说明,每个可以是未取代的或者被一个或多个取代基所取代的,所述取代基选自但不限于卤素、羟基、烷氧基、烷基硫基、C1-C6酰基、甲酰基、氰基、芳基氧基或芳基,只要所述取代基是空间上相容的且满足化学键合和应变能规则。术语“烯基”和“炔基”意在包括一个或多个不饱和键。
如本申请所用,术语“芳基烷基”指具有总计7至11个碳原子的苯基取代的烷基,例如苄基(–CH2C6H5)、2-甲基萘基(–CH2C10H7)和1-或2-苯乙基(–CH2CH2C6H5或–CH(CH3)C6H5)。所述苯基自身可以是未取代的或者被一个或多个取代基所取代的,所述取代基选自卤素、硝基、氰基、C1-C6烷基、C1-C6烷氧基、卤代的C1-C6烷基、卤代的C1-C6烷氧基、C1-C6烷基硫基、C(O)OC1-C6烷基或者其中两个相邻取代基一起成为–O(CH2)nO–(其中n=1或2),只要所述取代基是空间上相容的且满足化学键合和应变能规则。
除非另有具体限定,术语“卤素”以及衍生术语例如“卤代”,指氟、氯、溴和碘。
被1至4个独立地选自卤素、C1-C4烷基、卤代C1-C4烷基、C1-C4烷氧基或卤代C1-C4烷氧基的取代基所取代的苯基可以具有任何定位,但是优选4-取代的苯基异构体、2,4-二取代的苯基异构体、2,3,4-三取代的苯基异构体、2,4,5-三取代的苯基异构体和2,3,4,6-四取代的苯基异构体。
4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯是通过一系列步骤从3,4,5,6-四氯吡啶-2-甲腈制备的,所述步骤包括氟交换、胺化、与肼反应、卤化、水解、酯化和过渡金属辅助的偶联。个别步骤可以以不同的顺序来进行。
3,4,5,6-四氯吡啶-2-甲腈起始物质是已知的化合物且是可商购的。
在氟化物交换反应中,氟化的吡啶-2-甲腈是通过使得相应的氯化吡啶-2-甲腈与对于所要交换的每个环氯取代基而言大约一个当量的氟离子源反应来制备的。
典型的氟离子源是碱金属氟化物,其包括氟化钠(NaF)、氟化钾(KF)和氟化铯(CsF),优选KF和CsF。烷基的或芳基的季铵或季鏻氟化物也可以作为氟化物源或作为添加剂来使用。优选地,所述反应在极性非质子性溶剂或反应介质中进行,例如二甲基亚砜(DMSO)、N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)、六甲基磷酰胺(HMPA)或二氧噻吩烷。反应进行的温度不是决定性的但通常是在60℃至180℃且优选地在70℃至80℃。取决于具体反应中所用的溶剂,最适温度将会改变。一般而言,温度越低反应将会进行得越慢。本反应典型地在剧烈搅拌下进行,所述搅拌足以保持基本上均一分散的反应物的混合物。
在进行氟化反应中,反应物的比率和加入次序都不是决定性的。通常,在向反应混合物加入氯化吡啶-2-甲腈之前将溶剂与碱金属氟化物混合。典型的反应一般需要2至100小时,优选地需要3至6小时且通常在环境大气压进行。
尽管反应物的精确量不是决定性的,但是优选使用将供给基于起始物质中所要交换氯原子的数目而言至少等摩尔量的氟原子的量的碱金属氟化物,即,至少等摩尔量的碱金属氟化物。反应完成后,通过使用标准的分离和纯化技术例如蒸馏、结晶或色谱法重新得到期望的产物。
在典型的氟化物交换中,获得产物的混合物,其包括显著量的过度氟化的副产物3,4,5,6-四氟吡啶-2-甲腈(式H)。
期望的3-氯-4,5,6-三氟吡啶-2-甲腈的最终产率可通过以下方法来提高:分离过度氟化的副产物3,4,5,6-四氟吡啶-2-甲腈并将其重复利用以生成可经受氟化物交换反应的中间体。这可以在若干天内完成。3,4,5,6-四氟吡啶-2-甲腈与LiCl的反应或3,4,5,6-四氟吡啶-2-甲腈与过量3,4,5,6-四氯吡啶-2-甲腈的反应或两者的组合,在含有或不含有溶剂的情况下,都产生氯代-氟代吡啶-2-甲腈,其中3-氯代异构体可用作形成期望产物的起始物质。因此3,4,5,6-四氟吡啶-2-甲腈可以与过量LiCl加热以生成主要是3,4,5-三氯-6-氟吡啶-2-甲腈和四氯吡啶-2-甲腈的混合物。在另一技术中,在相转移催化剂存在下,使得分离出的3,4,5,6-四氟吡啶-2-甲腈与过量3,4,5,6-四氯吡啶-2-甲腈反应,生成主要由一氟-三氯吡啶-2-甲腈和二氟-二氯吡啶-2-甲腈组成的混合物。最后,在相转移催化剂存在下,分离出的3,4,5,6-四氟吡啶-2-甲腈与3,4,5,6-四氯吡啶-2-甲腈的等量混合物和1至3当量的LiCl生成主要是3,4,5-三氯-6-氟吡啶-2-甲腈和3,4,5,6-四氯吡啶-2-甲腈的混合物。这些主要由一氟-三氯吡啶-2-甲腈和/或二氟-二氯吡啶-2-甲腈组成的混合物,在使用碱金属氟化物的氟化反应中是有用的,以由3,4,5,6-四氟吡啶-2-甲腈制备3-氯-4,5,6-三氟吡啶-2-甲腈。
在逆向卤素交换反应中,将3,4,5,6-四氟吡啶-2-甲腈与5至10当量的LiCl加热,优选与6当量的LiCl加热以生成4,5-二氯-3,6-二氟吡啶-2-甲腈(3,6-F2-PN)、6-氟-3,4,5-三氯吡啶-2-甲腈(6-F-PN)和3,4,5,6-四氯吡啶-2-甲腈(Cl4-PN)的混合物。所述反应可无溶剂或在极性非质子性溶剂或反应介质中进行,例如DMSO、NMP、DMF、HMPA或二氧噻吩烷。在溶剂中进行反应往往是方便的。反应进行的温度不是决定性的但通常是在80℃至200℃且优选100℃至150℃。
通过经氟交换反应重复利用混合物,90%或更多的混合物对形成3-氯-4,5,6-三氟吡啶-2-甲腈是有用的。
在氟和氯基团互换的置换反应中,使得3,4,5,6-四氟吡啶-2-甲腈与1至3当量的3,4,5,6-四氯吡啶-2-甲腈反应,优选与2当量的3,4,5,6-四氯吡啶-2-甲腈反应。所述反应可无溶剂或在极性非质子性溶剂或反应介质中进行,例如DMSO、NMP、DMF、HMPA或二氧噻吩烷。不用溶剂进行反应往往是方便的。所述置换反应在添加剂存在下进行。添加剂包括(a)含10个或更多碳原子的季鏻盐和(b)通常称作冠醚的大环聚醚。适合的冠醚催化剂包括,但不限于,18-冠-6;二环己烷-18-冠-6;二苯并-18-冠-6;15-冠-5。适合的季鏻盐包括特别优选的四正烷基鏻盐。反应进行的温度不是决定性的但通常是在80℃至200℃且优选150℃至180℃。
在典型的置换反应中,例如,其中允许1当量的3,4,5,6-四氟吡啶-2-甲腈与2当量的3,4,5,6-四氯吡啶-2-甲腈反应,获得下列异构体的混合物:3,4,5,6-四氯吡啶-2-甲腈(Cl4-PN)、3,5-二氯-4,6-二氟吡啶-2-甲腈(4,6-F2-PN)、3,4-二氯-5,6-二氟吡啶-2-甲腈(5,6-F2-PN)、4,5-二氯-3,6-二氟吡啶-2-甲腈(3,6-F2-PN)、6-氟-3,4,5-三氯吡啶-2-甲腈(6-F-PN)和4-氟-3,5,6-三氯吡啶-2-甲腈(4-F-PN)。
通过经氟交换反应重复利用混合物,80%的混合物对形成3-氯-4,5,6-三氟吡啶-2-甲腈是有用的。
在逆向卤素交换反应和置换反应的组合中,允许3,4,5,6-四氟吡啶-2-甲腈与1至3当量的3,4,5,6-四氯吡啶-2-甲腈反应,优选与1当量的3,4,5,6-四氯-吡啶-2-甲腈反应,并与1至4当量的LiCl反应,优选与1.5至2.5当量的LiCl反应。所述反应可无溶剂或在极性非质子性溶剂或反应介质中进行,例如DMSO、NMP、DMF、HMPA或二氧噻吩烷。不用溶剂进行反应往往是方便的。所述置换反应在添加剂存在下进行。添加剂包括(a)含10个或更多碳原子的季鏻盐和(b)通常称作冠醚的大环聚醚。适合的冠醚催化剂包括,但不限于,18-冠-6;二环己烷-18-冠-6;二苯并-18-冠-6;15-冠-5。适合的季鏻盐包括特别优选的四正烷基鏻盐。反应进行的温度不是决定性的但通常是在80℃至200℃且优选150℃至180℃。
在逆向卤素交换和置换反应的典型组合中,例如,允许1当量的3,4,5,6-四氟吡啶-2-甲腈与1当量的3,4,5,6-四氯吡啶-2-甲腈及1.5当量的LiCl反应,并获得下列异构体的混合物:
通过经氟交换反应重复利用混合物,92%的混合物对形成3-氯-4,5,6-三氟吡啶-2-甲腈是有用的。
在胺化反应中,允许4-氟吡啶-2-甲腈与氨反应以用氨基替换氟原子。
尽管仅需要化学量的氨,但使用大量过量的氨往往是方便的。使用氨既作为反应物又作为中和反应生成的氟化氢(HF)的碱往往是方便的。可替换地,氨可以是溶液形式,例如氢氧化铵的水溶液。所述反应不用溶剂或在惰性溶剂中进行。如果使用溶剂,惰性溶剂包括,但不限于,醇、醚、酯、酮、DMSO和芳族溶剂。反应进行的温度不是决定性的但通常是在0℃至45℃且优选10℃至30℃。
典型的反应一般需要0.5至5小时且通常在环境大气压进行。通过使用标准的分离和纯化技术重新得到期望的产物。
在与肼的反应中,允许6-氟吡啶-2-甲腈与肼反应以用肼基替换氟原子。
尽管仅需要化学量的肼,但使用过量的肼往往是方便的,既作为反应物又作为中和反应形成的HF的碱。优选肼是一水合物。所述反应在惰性极性溶剂例如DMSO、DMF、NMP、乙腈、含氯溶剂、醚、四氢呋喃(THF)或醇中进行。优选DMSO和THF的混合物。反应进行的温度不是决定性的但通常是在室温至150℃且优选35℃至70℃。
在进行与肼的反应中,将肼溶于溶剂并向反应混合物中加入6-氟吡啶-2-甲腈。典型的反应一般需要0.5至5小时且通常在大气压进行。通过使用标准的分离和纯化技术重新得到期望的产物。通过用乙腈稀释反应混合物然后过滤可容易地分离出所述化合物。
在卤化反应中,6-卤代吡啶-2-甲腈是通过使得相应的6-肼基吡啶-2-甲腈与至少一个当量的溴化剂、氯化剂或碘化剂反应来制备的。
适合的碘化剂、氯化剂和溴化剂包括但不限于碘、一氯化碘、氯、溴、磺酰氯和磺酰溴。尽管仅需要化学量的卤化剂,但使用过量的卤化剂往往是方便的。所述反应在惰性非质子性溶剂中进行。可以使用多种溶剂例如含氯溶剂、乙腈、DMSO、二噁烷、DMF和水。通常优选使用含氯溶剂。反应进行的温度不是决定性的但通常是在室温至100℃且优选在室温至50℃。
在进行卤化反应中,将6-肼基吡啶-2-甲腈溶于或悬浮于溶剂中并向反应混合物中加入卤化剂。典型的反应一般需要0.5至24小时。通过使用标准的分离和纯化技术重新得到期望的产物。
在水解和酯化反应中,在路易斯酸或布朗斯台德酸存在下,允许吡啶-2-甲腈与醇(R1OH)反应。
布朗斯台德酸包括但不限于酸例如盐酸、硫酸和磷酸。路易斯酸包括三氟化硼、四卤化钛、四醇钛、卤化锌、卤化锡及五氟化磷和五氟化锑。典型地使用化学量的酸例如硫酸或磷酸。所述反应在期望的酯的C1-C12烷基醇或者未取代的或取代的C7-C11芳基烷基醇中进行。如果反应温度在醇溶剂的沸点以上,反应可方便地在密封反应器中进行。在进行酯化中,将吡啶-2-甲腈或水解中间体吡啶-2-甲酰胺加入到醇和酸的混合物中。虽然反应的温度不是决定性的,但往往从80℃加热至140℃且保持2至24小时,优选从100℃加热至120℃且保持6至8小时。通过使用标准的分离和纯化技术重新得到期望的产物。
在偶联反应中,允许6-卤代吡啶-2-甲酸酯与芳基金属化合物、烷基金属化合物或烯基金属化合物在过渡金属催化剂存在下反应,其中所述金属是Zn-卤化物、Zn-R、三-(C1-C4烷基)锡、铜或B(OR2)(OR3),其中R2和R3彼此独立地是氢、C1-C4烷基或一起形成亚乙基或亚丙基。
“催化剂”是过渡金属催化剂,具体而言是钯催化剂例如二乙酸钯或二(三苯基膦)二氯化钯(II),或者是镍催化剂例如乙酰丙酮镍(II)或二(三苯基膦)二氯化镍(II)。除此之外,催化剂可以从金属盐和配体原位制备,例如乙酸钯(II)和三苯基膦或者二氯化镍(II)和三苯基膦。这些原位催化剂可以通过先前的金属盐和配体的反应来制备,其后是加入到反应混合物中,或是直接向反应混合物中分开加入金属盐和配体。
典型地,在没有氧的条件下使用惰性气体例如氮气或氩气进行偶联反应。用来从偶联反应混合物中排除氧的技术,例如用惰性气体鼓泡,是本领域的技术人员所熟知的。这些技术的实例在The Manipulation of Air-SensitiveCompounds,2nd ed.,D.F.Shriver,M.A.Drezdzon,Eds.;Wiley-Interscience,1986中有描述。使用亚化学量的催化剂,典型地是0.0001当量至0.1当量。可以任选地加入另外量的配体以增加催化剂稳定性和活性。除此之外,典型地向偶联反应中加入添加剂例如碳酸钠、碳酸钾、氟化钾、氟化铯和氟化钠。所述偶联反应一般需要1至5当量这种添加剂,优选地是1至2当量。可以任选地向偶联反应中加入水以增加这些添加剂的可溶性。所述偶联反应一般需要1至3当量的芳基金属化合物、烷基金属化合物或烯基金属化合物,优选地是1至1.5当量。反应在惰性溶剂中进行,例如甲苯、THF、二噁烷或乙腈。进行反应的温度不是决定性的但通常是在25℃至150℃并优选地在50℃至125℃。典型的反应一般需要0.5至24小时。典型地加入反应物不需要特定的次序。往往操作上较为简单的是:组合除催化剂之外的所有反应物然后使反应溶液脱氧。脱氧之后,加入催化剂以开始偶联反应。
当芳基金属化合物、烷基金属化合物或烯基金属化合物的Met部分是Zn-卤化物、Zn-R或铜时,反应官能团的保护可能是必要的。例如,如果存在氨基取代基(-NHR或–NH2),可能需要这些反应基团的保护。多种用于保护氨基免于与有机金属试剂反应的基团是本领域中已知的。这些保护基团的实例在Protective Groups in Organic Synthesis,3rd ed.,T.W.Greene,P.G.M.Wuts,Eds.;Wiley-Interscience,1999中有描述。R-Met中使用的金属的选择受多种因素影响,例如成本、稳定性、反应性和保护反应官能团的需要。
通过这些方法中的任意一个获得的产物,可通过常规手段重新得到,例如蒸发或萃取,并可通过标准操作步骤纯化,例如通过重结晶或色谱法。
提出下列实施例以示例说明本发明。
实施例
氟交换
实施例1a3-氯-4,5,6-三氟吡啶-2-甲腈
氮气下将DMSO(3820毫升(mL))、粉末状的碳酸钾(K2CO3;42克(g))和细磨的氟化铯(CsF;1510g)装入5-升(L)机械搅拌的烧瓶中。通过在75-80℃(3.5mmHg,0.46kPa)蒸馏除去DMSO(大约1L)。在细磨的3,4,5,6-四氯吡啶-2-甲腈(685g)加入之前,在氮气下将淤浆冷却至55℃。加入历时15分钟(min)同时冷却以保持反应温度在74℃以下。在慢的氮气流下将温度控制在65-70℃且保持4小时(h)。将反应混合物冷却至40-50℃并将其倾入冰水(H2O;15L)和乙醚(Et2O;3L)混合物中。分离有机相后,用Et2O(2x2L)萃取水相。合并有机萃取物,以硫酸镁(MgSO4)干燥,过滤并通过在大气压蒸馏浓缩,得到粗产物混合物(469g),其为浅棕色油。该油与类似制备的另外的材料合并,得到总计1669g粗产物。使用30板(tray)Oldershaw柱在80-90℃温度范围将该油真空蒸馏得到63、13和2mm Hg(8.4,1.7和0.27kPa)收集的馏分。在13mm收集物质,得到457克(22%产率)作为两种一氯三氟吡啶-2-甲腈的93/7混合物的固体。将该固体在5℃从己烷(420g)和Et2O的混合物中重结晶,得到3-氯-4,5,6-三氟吡啶-2-甲腈(354克,98%纯度),其为白色细针状物。将少量样品第二次重结晶得到经气相色谱法(GC)的99.7%纯度:mp41.5–43℃;19F NMR(376MHz,CDCl3)δ-78.1(t,JF-F=23.1Hz,F6),-114.2(dd,JF-F=18.5,22.5Hz,F4),-149.3(dd,JF-F=18.2,22.6Hz,F5);13C{1H}NMR(101MHz,CDCl3)δ154.5(ddd,JF-C=270,11,7Hz,C4),151.3(ddd,JF-C=247,13,5Hz,C6),138.0(ddd,JF-C=279,31,13Hz,C5),124.7(ddd,JF-C=16,6,2Hz,C3),124.4(ddd,JF-C=16,7,2Hz,C2),112.2(s,CN);EIMS m/z192([M]+)。C6ClF3N2的分析计算值:C,37.43;N,14.55。实测值:C,36.91;N;14.25.
蒸馏的第一部分(63mm Hg,8.4kPa)得到纯的3,4,5,6-四氟-吡啶-2-甲腈(525g,24%),其为无色油:19F NMR(376MHz,CDCl3)δ-77.6(t,JF-F=23.8Hz,F6),-133.7(q,JF-F=18.8Hz,F4),-134.2(ddd,JF-F=24.2,18.6,10.1Hz,F3),-145.3(ddd,JF-F=24.1,18.2,10.2Hz,F5);13C{1H}NMR(101MHz,CDCl3)δ150.4(dm,JF-C=272Hz,C3),148.5(ddd,JF-C=245,12,4Hz,C6),147.3(dm,JF-C=270Hz,C4),138.6(ddd,JF-C=280,33,11Hz,C5),113.4(m,C2),110.20(s,CN).
蒸馏的第三部分(2mm Hg,0.27kPa)得到3,5-二氯-4,6-二氟-吡啶-2-甲腈(48g,98%纯度),其为白色固体:mp78-79℃;19F NMR(376MHz,CDCl3)δ-63.65(d,JF-F=18.7Hz,F6),-92.52(d,JF-F=18.5Hz,F4);13C{1H}NMR(101MHz,CDCl3)δ162.6(dd,JF-C=269,6Hz,C4),157.8(dd,JF-C=245,5Hz,C6),127.6(dd,JF-C=17,3Hz,C3),123.5(dd,JF-C=18,6Hz,C2),112.4(dd,JF-C=36,21Hz,C5),112.3(CN).
实施例1b3,4,5,6-四氟吡啶-2-甲腈与氯化锂的逆向卤素交换反应
将3,4,5,6-四氟吡啶-2-甲腈(17g,0.1摩尔(mol))与无水LiCl(25.4g,0.6mol)的混合物在无水DMSO(200mL)中加热。通过GC分析从H2O中萃取至Et2O中的等分试样来监测反应。最初将反应混合物加热至120℃且所有LiCl溶解。在120℃保持5分钟后,消耗所有的起始物质和一氯三氟-PN异构体得到3,6-F2-PN(83%)和6-F-PN(14%)的混合物。将反应温度升高至135℃并在总计75分钟后通过GC进行分析。测得所述混合物是3,6-F2-PN/6-F-PN/Cl4-PN的8:80:12混合物。
实施例1ca3,4,5,6-四氟吡啶-2-甲腈的置换
氮气下将3,4,5,6-四氯吡啶-2-甲腈(16.1g,66毫摩尔(mmol))和3,4,5,6-四氟吡啶-2-甲腈(5.9g,33mmol)的混合物加热至160℃以形成溶液。向该搅拌的溶液中加入四丁基氯化鏻(Bu4PCl;0.36g,1.2mmol),且将该溶液控制在160℃且保持1h。将等分试样溶于二氯甲烷(CH2Cl2)并在GC分析之前经过短的硅胶垫。卤代的吡啶-2-甲腈的特征是:11.2%Cl4-PN;11.3%4,6-F2-PN;2.3%5,6-F2-PN;19%3,6-F2-PN;52.6%6-F-PN和3.6%4-F-PN。80%的混合物在生成3-氯-4,5,6-三氟吡啶-2-甲腈的卤素交换反应中是有用的。
实施例1cb从3456-四氟吡啶-2-甲腈置换的重新利用
将细磨的CsF(35.1g,0.23mol)和无水DMSO(175mL)装入配备有短程蒸馏头的反应烧瓶中。将反应器搅拌并在真空(0.1mm)加热至70-75℃直至蒸去DMSO(75mL)。将该淤浆在氮气下冷却至50℃,并加入来自上面反应的热反应混合物(21.7g)。良好搅拌下将反应混合物加热至70℃且保持2.5h。将加到水中的等分试样的乙醚萃取物经GC检测发现其含有:61%3,4,5,6-四氟吡啶-2-甲腈;31%3-氯-4,5,6-三氟吡啶-2-甲腈;3.4%5-氯-3,5,6-三氟吡啶-2-甲腈和4.8%3,5-二氯-4,6-二氟吡啶-2-甲腈。这可有利地与当类似的反应用纯的3,4,5,6-四氯吡啶-2-甲腈起始时典型的38-42%粗略GC纯度相比。
实施例1d3,4,5,6-四氟吡啶-2-甲腈的LiCl辅助置换
氮气下将3,4,5,6-四氯吡啶-2-甲腈(12.2g,50mmol)和3,4,5,6-四氟吡啶-2-甲腈(8.8g,50mmol)的混合物加热至160℃,得到澄清溶液。向该溶液中加入Bu4PCl(0.36g,1.2mmol)。在加入无水LiCl(4.2g,0.1mol)之前将反应溶液控制在160℃且保持15分钟。60分钟后加入更多的LiCl(2.2g,50mmol),并将反应混合物搅拌11h。来自水的醚萃取物的GC分析显示是3,6-F2-PN/6-F-PN/Cl4-PN的8:75:17混合物。
胺化
实施例24-氨基-3-氯-5,6-二氟吡啶-2-甲腈
将3-氯-4,5,6-三氟吡啶-2-甲腈(200g)在乙酸乙酯中的溶液(EtOAc;3L)冷却至10℃。向该溶液中慢慢加入14%氢氧化铵水溶液(NH4OH;1296g)并保持温度在18-23℃。将水溶液从有机溶液中分离。依次用饱和NaCl水溶液与水的50/50溶液(500mL)及饱和NaCl水溶液(250mL)洗涤有机相。在50℃将有机相真空浓缩至500mL体积同时产物结晶出来。向该淤浆中加入庚烷(1L),并真空除去剩余的EtOAc,得到最终淤浆。经过滤收集固体。将该固体用戊烷洗涤并真空干燥,得到4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(173.8g,90%,99.6%纯度),其为白色结晶状固体:mp190–191.5℃;13C{1H}NMR(101MHz,DMSO-d6)δ150.03(dd,J=232.4,12.5Hz,C6),144.29(dd,J=11.4,6.9Hz,C4),133.72(dd,J=257.9,30.8Hz,C5),122.14(dd,J=19.6,4.9Hz,C2),119.31(s,C3),114.25(s,CN);19F NMR(376MHz,DMSO-d6)δ-91.24(d,J=24.2Hz),-154.97(d,J=24.2Hz);EIMS m/z189([M]+)。C6H2ClF2N3的分析计算值:C,38.02;H,1.06;N,22.17。实测值:C.37.91;H.1.00;22.02.
与肼反应
实施例34-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈
向水合肼(3.9g,78mmol)在THF(15mL)和DMSO(10mL)中的溶液中加入4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(5g,26mmol)在DMSO(5mL)中的溶液。将该溶液加热至65℃且保持45分钟,冷却并用乙腈(30mL)稀释,使产物沉淀成浅黄褐色固体。该固体在40℃真空干燥3h,得到4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(5.1g,98%):mp215–220℃dec;1H NMR(400MHz,DMSO-d6)7.9(br,1H),6.5(br,2H),4.0(br,2H);13C{1H}NMR(101MHz,DMSO-d6)δ149.34(d,J=10.5Hz,C6),138.28(d,J=11.6Hz,C4),133.81(d,J=251.6Hz,C5),123.74(d,J=5.3Hz,C2),115.87(s,C3),112.57(s,CN);19F NMR(376MHz,DMSO-d6)δ-154.6;ESIMS m/z203([M+H]+)。C6H5ClFN5的分析计算值:C,35.75;H,2.50;N,34.74。实测值:C,35.97;H,2.70:N,35.01.
卤化
实施例44-氨基-3,6-二氯-5-氟吡啶-2-甲腈
向4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(9.04g,44.8mmol)在CH2Cl2(150mL)中的混悬液中加入磺酰氯(7.20mL,89mmol)。将混合物室温搅拌40h。减压除去溶剂,并将残余物用饱和碳酸氢钠水溶液(NaHCO3)和EtOAc分配。分离有机相,以Na2SO4干燥并过滤。将溶液浓缩并通过硅胶色谱纯化,得到产物(7.01g,76%),其为灰白色固体:1H NMR(300MHz,DMSO-d6)δ7.55(s,2H);13C NMR(101MHz,DMSO-d6)δ143.26(d,J=259.2Hz,C5),142.69(d,J=14.0Hz,C4),135.53(d,J=17.6Hz.C6),126.07(d,J=4.4Hz,C2),120.14(d,J=4.3Hz,C3),114.36(s,CN);19F NMR(376MHz,DMSO-d6)δ-132.30(s);ESIMS m/z203([M+H]+),206.
水解和酯化
实施例54-氨基-3,6-二氯-5-氟吡啶-2-甲酸甲酯
向冷却的甲醇(8mL)中慢慢加入浓硫酸(2.0mL,37.5mmol)。然后向溶液中加入4-氨基-3,6-二氯-5-氟吡啶-2-甲腈(0.20g,0.97mmol),并将混合物搅拌回流29h。真空除去溶剂,将残余物倾入冰中并搅拌15分钟。用EtOAc(3x)萃取产物。合并有机萃取物,用盐水洗涤,以MgSO4干燥,过滤并通过硅胶柱纯化,得到4-氨基-3,6-二氯-5-氟吡啶-2-甲酸甲酯(0.085g,37%)白色固体:1H NMR(400MHz,CDCl3)δ5.08(s,2H),3.97(s,3H);13C NMR(101MHz,CDCl3)δ163.57(s,C=O),143.29(d,J=258.1Hz,C5),141.73(d,J=5.1Hz,C2),141.05(d,J=12.7Hz,C4),135.32(d,J=16.8Hz,C6),116.26(s,C3),53.24(s,OMe);19F NMR(376MHz,CDCl3)δ-135.63(s).
偶联
实施例6a4-氨基-3-氯-5-氟-6-(4-氯-2-氟-3-甲氧基-苯基)吡啶-2-甲酸 甲酯
将4-氨基-3,6-二氯-5-氟吡啶-2-甲酸甲酯(9.965g,41.7mmol)、2-(4-氯-2-氟-3-甲氧基苯基)-1,3,2-二氧杂环戊硼烷(12.74g,52.1mmol)和KF(4.84g,83mmol)装入具有回流冷凝管、氮气入口和热电偶的250mL三颈烧瓶中。加入乙腈(78mL)和水(26mL)。用氮气对反应混合物进行排气。加入二(三苯基膦)二氯化钯(II)(Pd(PPh3)2Cl2;1.477g,2.10mmol,5mol%),并在氮气下将溶液加热至70℃且保持2h。当冷却至室温时,过滤形成沉淀并用水洗涤。将沉淀溶于EtOAc(ca500mL)并用水、然后盐水洗涤。干燥有机相(MgSO4)并使用旋转蒸发仪除去溶剂,得到橙色固体,将其在50℃真空干燥箱中干燥(11.46g,76%产率):mp169–170.5℃;1H NMR(400MHz,DMSO-d6)δ7.48(d,J=8.4Hz,1H),7.32(t,J=7.7Hz,1H),7.15(s,2H),3.96(s,3H),3.90(s,3H);13C{1H}NMR(101MHz,DMSO-d6)δ164.85(s),153.11(d,J=252.5Hz),146.29(s),144.52(d,J=4.3Hz),143.74(s),142.75(dd,J=227.1,14.0Hz),136.38(d,J=13.4Hz),128.58(d,J=3.2Hz),125.87(s),125.54(d,J=3.5Hz),122.89(dd,J=13.8,4.0Hz),113.01(d,J=3.0Hz),61.61(d,J=4.2Hz),52.70(s);ESIMS m/z364([M+H]+)。C14H10Cl2F2N2O3的分析计算值:C,46.30;H,2.78;N,7.71。实测值:C,46.60;H,2.68;N,7.51.
实施例6b4-氨基-3-氯-5-氟-6-(4-氯-2-氟-3-甲氧基-苯基)吡啶-2-甲腈
将4-氨基-3,6-二氯-5-氟吡啶-2-甲腈(0.37g,1.80mmol)、2-(4-氯-2-氟-3-甲氧基苯基)-1,3,2-二氧杂环戊硼烷(0.549g,2.24mmol)和KF(0.209g,3.59mmol)的混合物吸收于乙腈(6.75mL)和水(2.25mL)。搅拌混合物并用氮气气氛鼓泡。加入Pd(PPh3)2Cl2(63mg,0.1mmol),并将混合物再次用氮气鼓泡。然后在氮气下将溶液加热至75℃且保持2h。当冷却下来时,沉淀形成并经由过滤收集,用水洗涤并真空干燥,得到产物(0.34g),其为灰白色固体。用EtOAc(3x)萃取水相,并用盐水洗涤合并的有机萃取物,干燥并浓缩。经硅胶色谱纯化,得到另外的产物(0.12g),其为白色固体。总产率78%。1H NMR(400MHz,DMSO-d6)δ7.50(dd,J=8.5,1.4Hz,1H),7.45(s,2H),7.33(dd,J=8.5,7.2Hz,1H),3.94(s,3H);13C{1H}NMR(101MHz,DMSO-d6)δ152.97(d,J=253.2Hz),145.73(d,J=260.8Hz),143.82(d,J=13.7Hz),141.83(d,J=14.7Hz),138.45(d,J=14.8Hz),133.93–132.79(m),128.93(d,J=3.3Hz),127.74(s),126.37–125.10(m),122.08(dd,J=13.6,3.9Hz),119.34(d,J=4.5Hz),114.99(s),61.61(s);19F NMR(376MHz,DMSO-d6)δ-129.00(dd,J=28.2,7.0Hz,1F),-133.76(d,J=28.2Hz,1F);ESIMS m/z330.1([M+H]+).

Claims (4)

1.式I的4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯的制备方法
其中
R表示C1-C4烷基、环丙基、C2-C4烯基或苯基,所述苯基被1至4个取代基所取代,所述取代基独立地选自卤素、C1-C4烷基、卤代C1-C4烷基、C1-C4烷氧基或卤代C1-C4烷氧基;和
R1表示C1-C12烷基或者未取代的或取代的C7-C11芳基烷基;
其中所述芳基烷基是苯基取代的烷基,其中所述苯基是未取代的或者被独立地选自下组的一个或多个取代基所取代的:卤素、硝基、氰基、C1-C6烷基、C1-C6烷氧基、卤代的C1-C6烷基、卤代的C1-C6烷氧基、C1-C6烷基硫基、C(O)OC1-C6烷基或者其中两个相邻取代基一起成为–O(CH2)nO–,其中n=1或2,只要所述取代基是空间上相容的且满足化学键合和应变能规则;
所述方法包括下列步骤:
a)用氟离子源氟化3,4,5,6-四氯吡啶-2-甲腈(式A)
以生成3-氯-4,5,6-三氟吡啶-2-甲腈(式B)
b)用氨胺化3-氯-4,5,6-三氟吡啶-2-甲腈(式B)以生成4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(式C)
c)使得4-氨基-3-氯-5,6-二氟吡啶-2-甲腈(式C)的6-位的氟取代基与肼反应以生成4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(式D)
d)用氯源、溴源或碘源卤化4-氨基-3-氯-5-氟-6-肼基吡啶-2-甲腈(式D)以生成式E的4-氨基-3-氯-5-氟-6-卤代-吡啶-2-甲腈
其中L是Br、Cl或I;
e)用强酸和式R1OH所示的醇水解并酯化式E的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲腈以生成式F的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲酸酯,
其中L和R1如先前所定义;和
f)将式F的4-氨基-3-氯-5-氟-6-卤代吡啶-2-甲酸酯与式G的芳基金属化合物、烷基金属化合物或烯基金属化合物在过渡金属催化剂存在下偶联以生成式I的4-氨基-3-氯-5-氟-6-(取代的)吡啶-2-甲酸酯,所述式G为:
R-Met                          G
其中R如先前所定义且Met表示Zn-卤化物、Zn-R、三-(C1-C4烷基)锡、铜或B(OR2)(OR3),其中R2和R3彼此独立地是氢、C1-C4烷基或一起形成亚乙基或亚丙基。
2.权利要求1的方法,其中步骤f)的偶联先于步骤e)的水解和酯化进行。
3.增加可回收的3-氯-4,5,6-三氟吡啶-2-甲腈(式B)的量的改进方法
所述3-氯-4,5,6-三氟吡啶-2-甲腈是用氟离子源通过氟化3,4,5,6-四氯吡啶-2-甲腈(式A)制备的
其中所述改进包括以下步骤:
i)分离来自氟化3,4,5,6-四氯吡啶-2-甲腈的过度氟化的3,4,5,6-四氟吡啶-2-甲腈(H)副产物
ii)使得分离出的3,4,5,6-四氟吡啶-2-甲腈(H)(a)与氯化锂(LiCl)反应,(b)在相转移催化剂存在下与3,4,5,6-四氯吡啶-2-甲腈(式A)反应或者(c)与LiCl和3,4,5,6-四氯吡啶-2-甲腈的组合反应以生成主要由3,4,5,6-四氯吡啶-2-甲腈、一氟-三氯吡啶-2-甲腈和二氟-二氯吡啶-2-甲腈组成的混合物;和
iii)将主要由3,4,5,6-四氯吡啶-2-甲腈、一氟-三氯吡啶-2-甲腈和二氟-二氯吡啶-2-甲腈组成的混合物重复利用到制备3-氯-4,5,6-三氟吡啶-2-甲腈(式B)的氟化反应中。
4.下式的化合物
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