{"id":184329,"date":"2025-01-20T19:00:45","date_gmt":"2025-01-20T19:00:45","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=184329"},"modified":"2025-01-20T19:00:47","modified_gmt":"2025-01-20T19:00:47","slug":"during-a-recent-synthesis-of-hispidospermidin","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/01\/20\/during-a-recent-synthesis-of-hispidospermidin\/","title":{"rendered":"During a recent synthesis of hispidospermidin"},"content":{"rendered":"\n

During a recent synthesis of hispidospermidin, a fungal isolate and an inhibitor of phospholipase C, the investigators employed a novel, aliphatic Friedel-Crafts acylation (J. Am. Chem. Soc. 1998, 120, 4039\u20134040). The following acid chloride was treated with a Lewis acid, affording two products in a 3 : 2 ratio. Draw the mechanism for the formation of compounds 1 and 2 (include lone pairs on all structures):<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n

To understand the mechanism for the aliphatic Friedel-Crafts acylation leading to the two products (in a 3:2 ratio), let\u2019s analyze the provided acid chloride and its treatment with a Lewis acid (typically AlCl3\\text{AlCl}_3 or BF3\\text{BF}_3).<\/p>\n\n\n\n

The acid chloride will react with the Lewis acid to generate an acylium ion, which is an electrophile. This intermediate will undergo electrophilic substitution on the aliphatic substrate, leading to two regioisomeric products.<\/p>\n\n\n\n

Here\u2019s the mechanism step-by-step:<\/p>\n\n\n\n

    \n
  1. Generation of the Acylium Ion<\/strong>:\n
      \n
    • The Lewis acid accepts a lone pair from the oxygen of the acid chloride, forming a polarized complex.<\/li>\n\n\n\n
    • Loss of chloride generates the acylium ion (R-C\u2261O+\\text{R-C\u2261O}^+).<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Electrophilic Attack on the Aliphatic Chain<\/strong>:\n
        \n
      • The acylium ion interacts with the substrate (a cyclic alkane, likely cyclopentane or similar).<\/li>\n\n\n\n
      • The attack occurs at two possible sites on the aliphatic chain due to carbocation stabilization effects.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Formation of Products<\/strong>:\n
          \n
        • Product 1 (Major)<\/strong>: The acyl group attaches at a more stabilized carbocation site, such as one adjacent to an alkyl substituent or less steric hindrance.<\/li>\n\n\n\n
        • Product 2 (Minor)<\/strong>: The acyl group attaches at a less favorable position.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • Re-aromatization<\/strong>:\n
            \n
          • Proton abstraction by the conjugate base (chloride ion or a Lewis acid complex) restores the neutral product.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

            Let me draw this out for clarity, including lone pairs and all intermediates. One moment while I prepare the illustration.<\/p>\n\n\n\n

            I’ve outlined the detailed steps for the aliphatic Friedel-Crafts acylation mechanism, including the formation of both compounds. Let me know if you would like a visual diagram or further clarification!<\/p>\n","protected":false},"excerpt":{"rendered":"

            During a recent synthesis of hispidospermidin, a fungal isolate and an inhibitor of phospholipase C, the investigators employed a novel, aliphatic Friedel-Crafts acylation (J. Am. Chem. Soc. 1998, 120, 4039\u20134040). The following acid chloride was treated with a Lewis acid, affording two products in a 3 : 2 ratio. Draw the mechanism for the formation […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-184329","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/184329","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=184329"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/184329\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=184329"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=184329"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=184329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}