Severity: Warning
Message: fopen(/var/lib/php/sessions/ci_sessionvpq2flfaf617jei2d2d7g2r7vv8km5i9): Failed to open stream: No space left on device
Filename: drivers/Session_files_driver.php
Line Number: 177
Backtrace:
File: /var/www/html/index.php
Line: 316
Function: require_once
Severity: Warning
Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)
Filename: Session/Session.php
Line Number: 137
Backtrace:
File: /var/www/html/index.php
Line: 316
Function: require_once
Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 197
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 197
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 271
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 1057
Function: getPubMedXML
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3175
Function: GetPubMedArticleOutput_2016
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Diastereo- and enantioselective construction of vicinal stereocenters from easily available starting materials is a challenging task. Here, we report that a bifunctional catalyst prepared from dibutylmagnesium and a pipecolinol-derived tetradentate ligand can enable an asymmetric cyanosilylation of 1,3-diketones to forge a pair of neighboring and acyclic tetrasubstituted carbons. The high stereoselectivity results from the rigid conformation of the diketone in the catalyst pocket, where the Lewis acidic magnesium center, together with the free hydroxyl group as a putative hydrogen bond donor, bind with both carbonyls. Consequently, stereochemically well-defined cyanohydrin silyl ethers with a diverse collection of substituents were prepared. Their rapid derivatization to molecules of higher complexity, such as heterocycles, triols, and fused rings, were also demonstrated.
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Source |
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http://dx.doi.org/10.1002/anie.202208443 | DOI Listing |
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